4.7.2 The iframe element

Categories:
Flow content.
Phrasing content.
Embedded content.
Interactive content.
Palpable content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Text that conforms to the requirements given in the prose.
Tag omission in text/html:
Neither tag is omissible.
Content attributes:
Global attributes
src — Address of the resource
srcdoc — A document to render in the iframe
name — Name of nested browsing context
sandbox — Security rules for nested content
seamless — Whether to apply the document's styles to the nested content
allowfullscreen — Whether to allow the iframe's contents to use requestFullscreen()
width — Horizontal dimension
height — Vertical dimension
DOM interface:
interface HTMLIFrameElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString srcdoc;
           attribute DOMString name;
  [PutForwards=value] readonly attribute DOMSettableTokenList sandbox;
           attribute boolean seamless;
           attribute boolean allowFullscreen;
           attribute DOMString width;
           attribute DOMString height;
  readonly attribute Document? contentDocument;
  readonly attribute WindowProxy? contentWindow;

  // also has obsolete members
};

The iframe element represents a nested browsing context.

The src attribute gives the address of a page that the nested browsing context is to contain. The attribute, if present, must be a valid non-empty URL potentially surrounded by spaces. If the itemprop is specified on an iframe element, then the src attribute must also be specified.

The srcdoc attribute gives the content of the page that the nested browsing context is to contain. The value of the attribute is the source of an iframe srcdoc document.

For iframe elements in HTML documents, the srcdoc attribute, if present, must have a value using the HTML syntax that consists of the following syntactic components, in the given order:

  1. Any number of comments and space characters.
  2. Optionally, a DOCTYPE.
  3. Any number of comments and space characters.
  4. The root element, in the form of an html element.
  5. Any number of comments and space characters.

For iframe elements in XML documents, the srcdoc attribute, if present, must have a value that matches the production labeled document in the XML specification. [XML]

Here a blog uses the srcdoc attribute in conjunction with the sandbox and seamless attributes described below to provide users of user agents that support this feature with an extra layer of protection from script injection in the blog post comments:

<article>
 <h1>I got my own magazine!</h1>
 <p>After much effort, I've finally found a publisher, and so now I
 have my own magazine! Isn't that awesome?! The first issue will come
 out in September, and we have articles about getting food, and about
 getting in boxes, it's going to be great!</p>
 <footer>
  <p>Written by <a href="/users/cap">cap</a>, 1 hour ago.
 </footer>
 <article>
  <footer> Thirteen minutes ago, <a href="/users/ch">ch</a> wrote: </footer>
  <iframe seamless sandbox srcdoc="<p>did you get a cover picture yet?"></iframe>
 </article>
 <article>
  <footer> Nine minutes ago, <a href="/users/cap">cap</a> wrote: </footer>
  <iframe seamless sandbox srcdoc="<p>Yeah, you can see it <a href=&quot;/gallery?mode=cover&amp;amp;page=1&quot;>in my gallery</a>."></iframe>
 </article>
 <article>
  <footer> Five minutes ago, <a href="/users/ch">ch</a> wrote: </footer>
  <iframe seamless sandbox srcdoc="<p>hey that's earl's table.
<p>you should get earl&amp;amp;me on the next cover."></iframe>
 </article>

Notice the way that quotes have to be escaped (otherwise the srcdoc attribute would end prematurely), and the way raw ampersands (e.g. in URLs or in prose) mentioned in the sandboxed content have to be doubly escaped — once so that the ampersand is preserved when originally parsing the srcdoc attribute, and once more to prevent the ampersand from being misinterpreted when parsing the sandboxed content.

Furthermore, notice that since the DOCTYPE is optional in iframe srcdoc documents, and the html, head, and body elements have optional start and end tags, and the title element is also optional in iframe srcdoc documents, the markup in a srcdoc attribute can be relatively succint despite representing an entire document, since only the contents of the body element need appear literally in the syntax. The other elements are still present, but only by implication.

In the HTML syntax, authors need only remember to use U+0022 QUOTATION MARK characters (") to wrap the attribute contents and then to escape all U+0022 QUOTATION MARK (") and U+0026 AMPERSAND (&) characters, and to specify the sandbox attribute, to ensure safe embedding of content.

Due to restrictions of the XHTML syntax, in XML the U+003C LESS-THAN SIGN character (<) needs to be escaped as well. In order to prevent attribute-value normalization, some of XML's whitespace characters — specifically U+0009 CHARACTER TABULATION (tab), U+000A LINE FEED (LF), and U+000D CARRIAGE RETURN (CR) — also need to be escaped. [XML]

If the src attribute and the srcdoc attribute are both specified together, the srcdoc attribute takes priority. This allows authors to provide a fallback URL for legacy user agents that do not support the srcdoc attribute.


When an iframe element is inserted into a document, the user agent must create a nested browsing context, and then process the iframe attributes for the "first time".

When an iframe element is removed from a document, the user agent must discard the nested browsing context.

This happens without any unload events firing (the nested browsing context and its Document are discarded, not unloaded).

Whenever an iframe element with a nested browsing context has its srcdoc attribute set, changed, or removed, the user agent must process the iframe attributes.

Similarly, whenever an iframe element with a nested browsing context but with no srcdoc attribute specified has its src attribute set, changed, or removed, the user agent must process the iframe attributes.

When the user agent is to process the iframe attributes, it must run the first appropriate steps from the following list:

If the srcdoc attribute is specified

Navigate the element's child browsing context to a resource whose Content-Type is text/html, whose URL is about:srcdoc, and whose data consists of the value of the attribute. The resulting Document must be considered an iframe srcdoc document.

Otherwise, if the element has no src attribute specified, and the user agent is processing the iframe's attributes for the "first time"

Queue a task to run the iframe load event steps.

The task source for this task is the DOM manipulation task source.

Otherwise
  1. If the value of the src attribute is missing, or its value is the empty string, let url be the string "about:blank".

    Otherwise, resolve the value of the src attribute, relative to the iframe element.

    If that is not successful, then let url be the string "about:blank". Otherwise, let url be the resulting absolute URL.

  2. If there exists an ancestor browsing context whose active document's address, ignoring fragment identifiers, is equal to url, then abort these steps.

  3. Navigate the element's child browsing context to url.

Any navigation required of the user agent in the process the iframe attributes algorithm must be completed as an explicit self-navigation override and with the iframe element's document's browsing context as the source browsing context.

Furthermore, if the active document of the element's child browsing context before such a navigation was not completely loaded at the time of the new navigation, then the navigation must be completed with replacement enabled.

Similarly, if the child browsing context's session history contained only one Document when the process the iframe attributes algorithm was invoked, and that was the about:blank Document created when the child browsing context was created, then any navigation required of the user agent in that algorithm must be completed with replacement enabled.

When a Document in an iframe is marked as completely loaded, the user agent must synchronously run the iframe load event steps.

A load event is also fired at the iframe element when it is created if no other data is loaded in it.

Each Document has an iframe load in progress flag and a mute iframe load flag. When a Document is created, these flags must be unset for that Document.

The iframe load event steps are as follows:

  1. Let child document be the active document of the iframe element's nested browsing context.

  2. If child document has its mute iframe load flag set, abort these steps.

  3. Set child document's iframe load in progress flag.

  4. Fire a simple event named load at the iframe element.

  5. Unset child document's iframe load in progress flag.

This, in conjunction with scripting, can be used to probe the URL space of the local network's HTTP servers. User agents may implement cross-origin access control policies that are stricter than those described above to mitigate this attack, but unfortunately such policies are typically not compatible with existing Web content.

When the iframe's browsing context's active document is not ready for post-load tasks, and when anything in the iframe is delaying the load event of the iframe's browsing context's active document, and when the iframe's browsing context is in the delaying load events mode, the iframe must delay the load event of its document.

If, during the handling of the load event, the browsing context in the iframe is again navigated, that will further delay the load event.

If, when the element is created, the srcdoc attribute is not set, and the src attribute is either also not set or set but its value cannot be resolved, the browsing context will remain at the initial about:blank page.

If the user navigates away from this page, the iframe's corresponding WindowProxy object will proxy new Window objects for new Document objects, but the src attribute will not change.


The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context. When the browsing context is created, if the attribute is present, the browsing context name must be set to the value of this attribute; otherwise, the browsing context name must be set to the empty string.

Whenever the name attribute is set, the nested browsing context's name must be changed to the new value. If the attribute is removed, the browsing context name must be set to the empty string.


The sandbox attribute, when specified, enables a set of extra restrictions on any content hosted by the iframe. Its value must be an unordered set of unique space-separated tokens that are ASCII case-insensitive. The allowed values are allow-forms, allow-pointer-lock, allow-popups, allow-same-origin, allow-scripts, and allow-top-navigation.

When the attribute is set, the content is treated as being from a unique origin, forms, scripts, and various potentially annoying APIs are disabled, links are prevented from targeting other browsing contexts, and plugins are secured. The allow-same-origin keyword causes the content to be treated as being from its real origin instead of forcing it into a unique origin; the allow-top-navigation keyword allows the content to navigate its top-level browsing context; and the allow-forms, allow-pointer-lock, allow-popups and allow-scripts keywords re-enable forms, the pointer lock API, popups, and scripts respectively. [POINTERLOCK]

Setting both the allow-scripts and allow-same-origin keywords together when the embedded page has the same origin as the page containing the iframe allows the embedded page to simply remove the sandbox attribute and then reload itself, effectively breaking out of the sandbox altogether.

These flags only take effect when the nested browsing context of the iframe is navigated. Removing them, or removing the entire sandbox attribute, has no effect on an already-loaded page.

Potentially hostile files should not be served from the same server as the file containing the iframe element. Sandboxing hostile content is of minimal help if an attacker can convince the user to just visit the hostile content directly, rather than in the iframe. To limit the damage that can be caused by hostile HTML content, it should be served from a separate dedicated domain. Using a different domain ensures that scripts in the files are unable to attack the site, even if the user is tricked into visiting those pages directly, without the protection of the sandbox attribute.

When an iframe element with a sandbox attribute has its nested browsing context created (before the initial about:blank Document is created), and when an iframe element's sandbox attribute is set or changed while it has a nested browsing context, the user agent must parse the sandboxing directive using the attribute's value as the input, the iframe element's nested browsing context's iframe sandboxing flag set as the output, and, if the iframe has an allowfullscreen attribute, the allow fullscreen flag.

When an iframe element's sandbox attribute is removed while it has a nested browsing context, the user agent must empty the iframe element's nested browsing context's iframe sandboxing flag set as the output.

In this example, some completely-unknown, potentially hostile, user-provided HTML content is embedded in a page. Because it is served from a separate domain, it is affected by all the normal cross-site restrictions. In addition, the embedded page has scripting disabled, plugins disabled, forms disabled, and it cannot navigate any frames or windows other than itself (or any frames or windows it itself embeds).

<p>We're not scared of you! Here is your content, unedited:</p>
<iframe sandbox src="http://usercontent.example.net/getusercontent.cgi?id=12193"></iframe>

It is important to use a separate domain so that if the attacker convinces the user to visit that page directly, the page doesn't run in the context of the site's origin, which would make the user vulnerable to any attack found in the page.

In this example, a gadget from another site is embedded. The gadget has scripting and forms enabled, and the origin sandbox restrictions are lifted, allowing the gadget to communicate with its originating server. The sandbox is still useful, however, as it disables plugins and popups, thus reducing the risk of the user being exposed to malware and other annoyances.

<iframe sandbox="allow-same-origin allow-forms allow-scripts"
        src="http://maps.example.com/embedded.html"></iframe>

Suppose a file A contained the following fragment:

<iframe sandbox="allow-same-origin allow-forms" src=B></iframe>

Suppose that file B contained an iframe also:

<iframe sandbox="allow-scripts" src=C></iframe>

Further, suppose that file C contained a link:

<a href=D>Link</a>

For this example, suppose all the files were served as text/html.

Page C in this scenario has all the sandboxing flags set. Scripts are disabled, because the iframe in A has scripts disabled, and this overrides the allow-scripts keyword set on the iframe in B. Forms are also disabled, because the inner iframe (in B) does not have the allow-forms keyword set.

Suppose now that a script in A removes all the sandbox attributes in A and B. This would change nothing immediately. If the user clicked the link in C, loading page D into the iframe in B, page D would now act as if the iframe in B had the allow-same-origin and allow-forms keywords set, because that was the state of the nested browsing context in the iframe in A when page B was loaded.

Generally speaking, dynamically removing or changing the sandbox attribute is ill-advised, because it can make it quite hard to reason about what will be allowed and what will not.


The seamless attribute is a boolean attribute. When specified, it indicates that the iframe element's browsing context is to be rendered in a manner that makes it appear to be part of the containing document (seamlessly included in the parent document).

An HTML inclusion is effected using this attribute as in the following example. In this case, the inclusion is of a site-wide navigation bar.

<!DOCTYPE HTML>
<title>Mirror Mirror — MovieInfo™</title>
<header>
 <h1>Mirror Mirror</h1>
 <p>Part of the MovieInfo™ Database</p>
 <nav>
  <iframe seamless src="nav.inc"></iframe>
 </nav>
</header>
...

An iframe element is said to be in seamless mode when all of the following conditions are met:

When an iframe element is in seamless mode, the following requirements apply:

If the attribute is not specified, or if the origin conditions listed above are not met, then the user agent should render the nested browsing context in a manner that is clearly distinguishable as a separate browsing context, and the seamless browsing context flag must be set to false for that browsing context.

It is important that user agents recheck the above conditions whenever the active document of the nested browsing context of the iframe changes, such that the seamless browsing context flag gets unset if the nested browsing context is navigated to another origin.

The attribute can be set or removed dynamically, with the rendering updating in tandem.

In this example, the site's navigation is embedded using a client-side include using an iframe. Any links in the iframe will, in new user agents, be automatically opened in the iframe's parent browsing context; for legacy user agents, the site could also include a base element with a target attribute with the value _parent. Similarly, in new user agents the styles of the parent page will be automatically applied to the contents of the frame, but to support legacy user agents authors might wish to include the styles explicitly.

<nav><iframe seamless src="nav.include.html"></iframe></nav>

The contenteditable attribute does not propagate into seamless iframes.


The allowfullscreen attribute is a boolean attribute. When specified, it indicates that Document objects in the iframe element's browsing context are to be allowed to use requestFullscreen() (if it's not blocked for other reasons, e.g. there is another ancestor iframe without this attribute set).


The iframe element supports dimension attributes for cases where the embedded content has specific dimensions (e.g. ad units have well-defined dimensions).

An iframe element never has fallback content, as it will always create a nested browsing context, regardless of whether the specified initial contents are successfully used.


Descendants of iframe elements represent nothing. (In legacy user agents that do not support iframe elements, the contents would be parsed as markup that could act as fallback content.)

When used in HTML documents, the allowed content model of iframe elements is text, except that invoking the HTML fragment parsing algorithm with the iframe element as the context element and the text contents as the input must result in a list of nodes that are all phrasing content, with no parse errors having occurred, with no script elements being anywhere in the list or as descendants of elements in the list, and with all the elements in the list (including their descendants) being themselves conforming.

The iframe element must be empty in XML documents.

The HTML parser treats markup inside iframe elements as text.


The IDL attributes src, srcdoc, name, sandbox, and seamless must reflect the respective content attributes of the same name.

The allowFullscreen IDL attribute must reflect the allowfullscreen content attribute.

The contentDocument IDL attribute must return the Document object of the active document of the iframe element's nested browsing context, if any and if its effective script origin is the same origin as the effective script origin specified by the incumbent settings object, or null otherwise.

The contentWindow IDL attribute must return the WindowProxy object of the iframe element's nested browsing context, if any, or null otherwise.

Here is an example of a page using an iframe to include advertising from an advertising broker:

<iframe src="http://ads.example.com/?customerid=923513721&amp;format=banner"
        width="468" height="60"></iframe>

4.7.3 The embed element

Categories:
Flow content.
Phrasing content.
Embedded content.
Interactive content.
Palpable content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Empty.
Tag omission in text/html:
No end tag.
Content attributes:
Global attributes
src — Address of the resource
type — Type of embedded resource
width — Horizontal dimension
height — Vertical dimension
Any other attribute that has no namespace (see prose).
DOM interface:
interface HTMLEmbedElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString type;
           attribute DOMString width;
           attribute DOMString height;
  legacycaller any (any... arguments);

  // also has obsolete members
};

Depending on the type of content instantiated by the embed element, the node may also support other interfaces.

The embed element provides an integration point for an external (typically non-HTML) application or interactive content.

The src attribute gives the address of the resource being embedded. The attribute, if present, must contain a valid non-empty URL potentially surrounded by spaces.

If the itemprop attribute is specified on an embed element, then the src attribute must also be specified.

The type attribute, if present, gives the MIME type by which the plugin to instantiate is selected. The value must be a valid MIME type. If both the type attribute and the src attribute are present, then the type attribute must specify the same type as the explicit Content-Type metadata of the resource given by the src attribute.

When the element is created with neither a src attribute nor a type attribute, and when attributes are removed such that neither attribute is present on the element anymore, and when the element has a media element ancestor, and when the element has an ancestor object element that is not showing its fallback content, any plugin instantiated for the element must be removed, and the embed element then represents nothing.

An embed element is said to be potentially active when the following conditions are all met simultaneously:

Whenever an embed element that was not potentially active becomes potentially active, and whenever a potentially active embed element that is remaining potentially active and has its src attribute set, changed, or removed or its type attribute set, changed, or removed, the user agent must queue a task using the embed task source to run the embed element setup steps.

The embed element setup steps are as follows:

  1. If another task has since been queued to run the embed element setup steps for this element, then abort these steps.

  2. If the element has a src attribute set

    The user agent must resolve the value of the element's src attribute, relative to the element. If that is successful, the user agent should fetch the resulting absolute URL, from the element's browsing context scope origin if it has one. The task that is queued by the networking task source once the resource has been fetched must run the following steps:

    1. If another task has since been queued to run the embed element setup steps for this element, then abort these steps.

    2. Determine the type of the content being embedded, as follows (stopping at the first substep that determines the type):

      1. If the element has a type attribute, and that attribute's value is a type that a plugin supports, then the value of the type attribute is the content's type.

      2. Otherwise, if applying the URL parser algorithm to the URL of the specified resource (after any redirects) results in a parsed URL whose path component matches a pattern that a plugin supports, then the content's type is the type that that plugin can handle.

        For example, a plugin might say that it can handle resources with path components that end with the four character string ".swf".

      3. Otherwise, if the specified resource has explicit Content-Type metadata, then that is the content's type.

      4. Otherwise, the content has no type and there can be no appropriate plugin for it.

    3. If the previous step determined that the content's type is image/svg+xml, then run the following substeps:

      1. If the embed element is not associated with a nested browsing context, associate the element with a newly created nested browsing context, and, if the element has a name attribute, set the browsing context name of the element's nested browsing context to the value of this attribute.

      2. Navigate the nested browsing context to the fetched resource, with replacement enabled, and with the embed element's document's browsing context as the source browsing context. (The src attribute of the embed element doesn't get updated if the browsing context gets further navigated to other locations.)

      3. The embed element now represents its associated nested browsing context.

    4. Otherwise, find and instantiate an appropriate plugin based on the content's type, and hand that plugin the content of the resource, replacing any previously instantiated plugin for the element. The embed element now represents this plugin instance.

    5. Once the resource or plugin has completely loaded, queue a task to fire a simple event named load at the element.

    Whether the resource is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the content's type and when handing the resource to the plugin.

    This allows servers to return data for plugins even with error responses (e.g. HTTP 500 Internal Server Error codes can still contain plugin data).

    Fetching the resource must delay the load event of the element's document.

    If the element has no src attribute set

    The user agent should find and instantiate an appropriate plugin based on the value of the type attribute. The embed element now represents this plugin instance.

    Once the plugin is completely loaded, queue a task to fire a simple event named load at the element.

The embed element has no fallback content. If the user agent can't find a suitable plugin when attempting to find and instantiate one for the algorithm above, then the user agent must use a default plugin. This default could be as simple as saying "Unsupported Format".

Whenever an embed element that was potentially active stops being potentially active, any plugin that had been instantiated for that element must be unloaded.

When a plugin is to be instantiated but it cannot be secured and the sandboxed plugins browsing context flag is set on the embed element's Document's active sandboxing flag set, then the user agent must not instantiate the plugin, and must instead render the embed element in a manner that conveys that the plugin was disabled. The user agent may offer the user the option to override the sandbox and instantiate the plugin anyway; if the user invokes such an option, the user agent must act as if the conditions above did not apply for the purposes of this element.

Plugins that cannot be secured are disabled in sandboxed browsing contexts because they might not honor the restrictions imposed by the sandbox (e.g. they might allow scripting even when scripting in the sandbox is disabled). User agents should convey the danger of overriding the sandbox to the user if an option to do so is provided.

When an embed element represents a nested browsing context: if the embed element's nested browsing context's active document is not ready for post-load tasks, and when anything is delaying the load event of the embed element's browsing context's active document, and when the embed element's browsing context is in the delaying load events mode, the embed must delay the load event of its document.

The task source for the tasks mentioned in this section is the DOM manipulation task source.

Any namespace-less attribute other than name, align, hspace, and vspace may be specified on the embed element, so long as its name is XML-compatible and contains no uppercase ASCII letters. These attributes are then passed as parameters to the plugin.

All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents.

The four exceptions are to exclude legacy attributes that have side-effects beyond just sending parameters to the plugin.

The user agent should pass the names and values of all the attributes of the embed element that have no namespace to the plugin used, when one is instantiated.

The HTMLEmbedElement object representing the element must expose the scriptable interface of the plugin instantiated for the embed element, if any. At a minimum, this interface must implement the legacy caller operation. (It is suggested that the default behavior of this legacy caller operation, e.g. the behavior of the default plugin's legacy caller operation, be to throw a NotSupportedError exception.)

The embed element supports dimension attributes.

The IDL attributes src and type each must reflect the respective content attributes of the same name.

Here's a way to embed a resource that requires a proprietary plugin, like Flash:

<embed src="catgame.swf">

If the user does not have the plugin (for example if the plugin vendor doesn't support the user's platform), then the user will be unable to use the resource.

To pass the plugin a parameter "quality" with the value "high", an attribute can be specified:

<embed src="catgame.swf" quality="high">

This would be equivalent to the following, when using an object element instead:

<object data="catgame.swf">
 <param name="quality" value="high">
</object>

4.7.4 The object element

Categories:
Flow content.
Phrasing content.
Embedded content.
If the element has a usemap attribute: Interactive content.
Listed, submittable, and reassociateable form-associated element.
Palpable content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Zero or more param elements, then, transparent.
Tag omission in text/html:
Neither tag is omissible.
Content attributes:
Global attributes
data — Address of the resource
type — Type of embedded resource
typemustmatch — Whether the type attribute and the Content-Type value need to match for the resource to be used
name — Name of nested browsing context
usemap — Name of image map to use
form — Associates the control with a form element
width — Horizontal dimension
height — Vertical dimension
DOM interface:
interface HTMLObjectElement : HTMLElement {
           attribute DOMString data;
           attribute DOMString type;
           attribute boolean typeMustMatch;
           attribute DOMString name;
           attribute DOMString useMap;
  readonly attribute HTMLFormElement? form;
           attribute DOMString width;
           attribute DOMString height;
  readonly attribute Document? contentDocument;
  readonly attribute WindowProxy? contentWindow;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  boolean reportValidity();
  void setCustomValidity(DOMString error);

  legacycaller any (any... arguments);

  // also has obsolete members
};

Depending on the type of content instantiated by the object element, the node also supports other interfaces.

The object element can represent an external resource, which, depending on the type of the resource, will either be treated as an image, as a nested browsing context, or as an external resource to be processed by a plugin.

The data attribute, if present, specifies the address of the resource. If present, the attribute must be a valid non-empty URL potentially surrounded by spaces.

Authors who reference resources from other origins that they do not trust are urged to use the typemustmatch attribute defined below. Without that attribute, it is possible in certain cases for an attacker on the remote host to use the plugin mechanism to run arbitrary scripts, even if the author has used features such as the Flash "allowScriptAccess" parameter.

The type attribute, if present, specifies the type of the resource. If present, the attribute must be a valid MIME type.

At least one of either the data attribute or the type attribute must be present.

If the itemprop attribute is specified on an object element, then the data attribute must also be specified.

The typemustmatch attribute is a boolean attribute whose presence indicates that the resource specified by the data attribute is only to be used if the value of the type attribute and the Content-Type of the aforementioned resource match.

The typemustmatch attribute must not be specified unless both the data attribute and the type attribute are present.

The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context, if applicable.

Whenever one of the following conditions occur:

...the user agent must queue a task to run the following steps to (re)determine what the object element represents. This task being queued or actively running must delay the load event of the element's document.

  1. If the user has indicated a preference that this object element's fallback content be shown instead of the element's usual behavior, then jump to the step below labeled fallback.

    For example, a user could ask for the element's fallback content to be shown because that content uses a format that the user finds more accessible.

  2. If the element has an ancestor media element, or has an ancestor object element that is not showing its fallback content, or if the element is not in a Document with a browsing context, or if the element's Document is not fully active, or if the element is still in the stack of open elements of an HTML parser or XML parser, or if the element is not being rendered, then jump to the step below labeled fallback.

  3. If the classid attribute is present, and has a value that isn't the empty string, then: if the user agent can find a plugin suitable according to the value of the classid attribute, and either plugins aren't being sandboxed or that plugin can be secured, then that plugin should be used, and the value of the data attribute, if any, should be passed to the plugin. If no suitable plugin can be found, or if the plugin reports an error, jump to the step below labeled fallback.

  4. If the data attribute is present and its value is not the empty string, then:

    1. If the type attribute is present and its value is not a type that the user agent supports, and is not a type that the user agent can find a plugin for, then the user agent may jump to the step below labeled fallback without fetching the content to examine its real type.

    2. Resolve the URL specified by the data attribute, relative to the element.

    3. If that failed, fire a simple event named error at the element, then jump to the step below labeled fallback.

    4. Fetch the resulting absolute URL, from the element's browsing context scope origin if it has one.

      Fetching the resource must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined next) has been run.

      For the purposes of the application cache networking model, this fetch operation is not for a child browsing context (though it might end up being used for one after all, as defined below).

    5. If the resource is not yet available (e.g. because the resource was not available in the cache, so that loading the resource required making a request over the network), then jump to the step below labeled fallback. The task that is queued by the networking task source once the resource is available must restart this algorithm from this step. Resources can load incrementally; user agents may opt to consider a resource "available" whenever enough data has been obtained to begin processing the resource.

    6. If the load failed (e.g. there was an HTTP 404 error, there was a DNS error), fire a simple event named error at the element, then jump to the step below labeled fallback.

    7. Determine the resource type, as follows:

      1. Let the resource type be unknown.

      2. If the object element has a type attribute and a typemustmatch attribute, and the resource has associated Content-Type metadata, and the type specified in the resource's Content-Type metadata is an ASCII case-insensitive match for the value of the element's type attribute, then let resource type be that type and jump to the step below labeled handler.

      3. If the object element has a typemustmatch attribute, jump to the step below labeled handler.

      4. If the user agent is configured to strictly obey Content-Type headers for this resource, and the resource has associated Content-Type metadata, then let the resource type be the type specified in the resource's Content-Type metadata, and jump to the step below labeled handler.

        This can introduce a vulnerability, wherein a site is trying to embed a resource that uses a particular plugin, but the remote site overrides that and instead furnishes the user agent with a resource that triggers a different plugin with different security characteristics.

      5. If there is a type attribute present on the object element, and that attribute's value is not a type that the user agent supports, but it is a type that a plugin supports, then let the resource type be the type specified in that type attribute, and jump to the step below labeled handler.

      6. Run the appropriate set of steps from the following list:

        If the resource has associated Content-Type metadata
        1. Let binary be false.

        2. If the type specified in the resource's Content-Type metadata is "text/plain", and the result of applying the rules for distinguishing if a resource is text or binary to the resource is that the resource is not text/plain, then set binary to true.

        3. If the type specified in the resource's Content-Type metadata is "application/octet-stream", then set binary to true.

        4. If binary is false, then let the resource type be the type specified in the resource's Content-Type metadata, and jump to the step below labeled handler.

        5. If there is a type attribute present on the object element, and its value is not application/octet-stream, then run the following steps:

          1. If the attribute's value is a type that a plugin supports, or the attribute's value is a type that starts with "image/" that is not also an XML MIME type, then let the resource type be the type specified in that type attribute.

          2. Jump to the step below labeled handler.

        Otherwise, if the resource does not have associated Content-Type metadata
        1. If there is a type attribute present on the object element, then let the tentative type be the type specified in that type attribute.

          Otherwise, let tentative type be the sniffed type of the resource.

        2. If tentative type is not application/octet-stream, then let resource type be tentative type and jump to the step below labeled handler.

      7. If applying the URL parser algorithm to the URL of the specified resource (after any redirects) results in a parsed URL whose path component matches a pattern that a plugin supports, then let resource type be the type that that plugin can handle.

        For example, a plugin might say that it can handle resources with path components that end with the four character string ".swf".

      It is possible for this step to finish, or for one of the substeps above to jump straight to the next step, with resource type still being unknown. In both cases, the next step will trigger fallback.

    8. Handler: Handle the content as given by the first of the following cases that matches:

      If the resource type is not a type that the user agent supports, but it is a type that a plugin supports

      If plugins are being sandboxed and the plugin that supports resource type cannot be secured, jump to the step below labeled fallback.

      Otherwise, the user agent should use the plugin that supports resource type and pass the content of the resource to that plugin. If the plugin reports an error, then jump to the step below labeled fallback.

      If the resource type is an XML MIME type, or if the resource type does not start with "image/"

      The object element must be associated with a newly created nested browsing context, if it does not already have one.

      If the URL of the given resource is not about:blank, the element's nested browsing context must then be navigated to that resource, with replacement enabled, and with the object element's document's browsing context as the source browsing context. (The data attribute of the object element doesn't get updated if the browsing context gets further navigated to other locations.)

      If the URL of the given resource is about:blank, then, instead, the user agent must queue a task to fire a simple event named load at the object element. No load event is fired at the about:blank document itself.

      The object element represents the nested browsing context.

      If the name attribute is present, the browsing context name must be set to the value of this attribute; otherwise, the browsing context name must be set to the empty string.

      In certain situations, e.g. if the resource was fetched from an application cache but it is an HTML file with a manifest attribute that points to a different application cache manifest, the navigation of the browsing context will be restarted so as to load the resource afresh from the network or a different application cache. Even if the resource is then found to have a different type, it is still used as part of a nested browsing context: only the navigate algorithm is restarted, not this object algorithm.

      If the resource type starts with "image/", and support for images has not been disabled

      Apply the image sniffing rules to determine the type of the image.

      The object element represents the specified image. The image is not a nested browsing context.

      If the image cannot be rendered, e.g. because it is malformed or in an unsupported format, jump to the step below labeled fallback.

      Otherwise

      The given resource type is not supported. Jump to the step below labeled fallback.

      If the previous step ended with the resource type being unknown, this is the case that is triggered.

    9. The element's contents are not part of what the object element represents.

    10. Abort these steps. Once the resource is completely loaded, queue a task to fire a simple event named load at the element.

  5. If the data attribute is absent but the type attribute is present, and the user agent can find a plugin suitable according to the value of the type attribute, and either plugins aren't being sandboxed or the plugin can be secured, then that plugin should be used. If these conditions cannot be met, or if the plugin reports an error, jump to the step below labeled fallback. Otherwise abort these steps; once the plugin is completely loaded, queue a task to fire a simple event named load at the element.

  6. Fallback: The object element represents the element's children, ignoring any leading param element children. This is the element's fallback content. If the element has an instantiated plugin, then unload it.

When the algorithm above instantiates a plugin, the user agent should pass to the plugin used the names and values of all the attributes on the element, in the order they were added to the element, with the attributes added by the parser being ordered in source order, followed by a parameter named "PARAM" whose value is null, followed by all the names and values of parameters given by param elements that are children of the object element, in tree order. If the plugin supports a scriptable interface, the HTMLObjectElement object representing the element should expose that interface. The object element represents the plugin. The plugin is not a nested browsing context.

Plugins are considered sandboxed for the purpose of an object element if the sandboxed plugins browsing context flag is set on the object element's Document's active sandboxing flag set.

Due to the algorithm above, the contents of object elements act as fallback content, used only when referenced resources can't be shown (e.g. because it returned a 404 error). This allows multiple object elements to be nested inside each other, targeting multiple user agents with different capabilities, with the user agent picking the first one it supports.

When an object element represents a nested browsing context: if the object element's nested browsing context's active document is not ready for post-load tasks, and when anything is delaying the load event of the object element's browsing context's active document, and when the object element's browsing context is in the delaying load events mode, the object must delay the load event of its document.

The task source for the tasks mentioned in this section is the DOM manipulation task source.

Whenever the name attribute is set, if the object element has a nested browsing context, its name must be changed to the new value. If the attribute is removed, if the object element has a browsing context, the browsing context name must be set to the empty string.

The usemap attribute, if present while the object element represents an image, can indicate that the object has an associated image map. The attribute must be ignored if the object element doesn't represent an image.

The form attribute is used to explicitly associate the object element with its form owner.

Constraint validation: object elements are always barred from constraint validation.

The object element supports dimension attributes.

The IDL attributes data, type and name each must reflect the respective content attributes of the same name. The typeMustMatch IDL attribute must reflect the typemustmatch content attribute. The useMap IDL attribute must reflect the usemap content attribute.

The contentDocument IDL attribute must return the Document object of the active document of the object element's nested browsing context, if any and if its effective script origin is the same origin as the effective script origin specified by the incumbent settings object, or null otherwise.

The contentWindow IDL attribute must return the WindowProxy object of the object element's nested browsing context, if it has one; otherwise, it must return null.

The willValidate, validity, and validationMessage attributes, and the checkValidity(), reportValidity(), and setCustomValidity() methods, are part of the constraint validation API. The form IDL attribute is part of the element's forms API.

All object elements have a legacy caller operation. If the object element has an instantiated plugin that supports a scriptable interface that defines a legacy caller operation, then that must be the behavior of the object's legacy caller operation. Otherwise, the object's legacy caller operation must be to throw a NotSupportedError exception.

In the following example, a Java applet is embedded in a page using the object element. (Generally speaking, it is better to avoid using applets like these and instead use native JavaScript and HTML to provide the functionality, since that way the application will work on all Web browsers without requiring a third-party plugin. Many devices, especially embedded devices, do not support third-party technologies like Java.)

<figure>
 <object type="application/x-java-applet">
  <param name="code" value="MyJavaClass">
  <p>You do not have Java available, or it is disabled.</p>
 </object>
 <figcaption>My Java Clock</figcaption>
</figure>

In this example, an HTML page is embedded in another using the object element.

<figure>
 <object data="clock.html"></object>
 <figcaption>My HTML Clock</figcaption>
</figure>

The following example shows how a plugin can be used in HTML (in this case the Flash plugin, to show a video file). Fallback is provided for users who do not have Flash enabled, in this case using the video element to show the video for those using user agents that support video, and finally providing a link to the video for those who have neither Flash nor a video-capable browser.

<p>Look at my video:
 <object type="application/x-shockwave-flash">
  <param name=movie value="http://video.example.com/library/watch.swf">
  <param name=allowfullscreen value=true>
  <param name=flashvars value="http://video.example.com/vids/315981">
  <video controls src="http://video.example.com/vids/315981">
   <a href="http://video.example.com/vids/315981">View video</a>.
  </video>
 </object>
</p>

4.7.5 The param element

Categories:
None.
Contexts in which this element can be used:
As a child of an object element, before any flow content.
Content model:
Empty.
Tag omission in text/html:
No end tag.
Content attributes:
Global attributes
name — Name of parameter
value — Value of parameter
DOM interface:
interface HTMLParamElement : HTMLElement {
           attribute DOMString name;
           attribute DOMString value;

  // also has obsolete members
};

The param element defines parameters for plugins invoked by object elements. It does not represent anything on its own.

The name attribute gives the name of the parameter.

The value attribute gives the value of the parameter.

Both attributes must be present. They may have any value.

If both attributes are present, and if the parent element of the param is an object element, then the element defines a parameter with the given name-value pair.

If either the name or value of a parameter defined by a param element that is the child of an object element that represents an instantiated plugin changes, and if that plugin is communicating with the user agent using an API that features the ability to update the plugin when the name or value of a parameter so changes, then the user agent must appropriately exercise that ability to notify the plugin of the change.

The IDL attributes name and value must both reflect the respective content attributes of the same name.

The following example shows how the param element can be used to pass a parameter to a plugin, in this case the O3D plugin.

<!DOCTYPE HTML>
<html lang="en">
  <head>
   <title>O3D Utah Teapot</title>
  </head>
  <body>
   <p>
    <object type="application/vnd.o3d.auto">
     <param name="o3d_features" value="FloatingPointTextures">
     <img src="o3d-teapot.png"
          title="3D Utah Teapot illustration rendered using O3D."
          alt="When O3D renders the Utah Teapot, it appears as a squat
          teapot with a shiny metallic finish on which the
          surroundings are reflected, with a faint shadow caused by
          the lighting.">
     <p>To see the teapot actually rendered by O3D on your
     computer, please download and install the <a
     href="http://code.google.com/apis/o3d/docs/gettingstarted.html#install">O3D plugin</a>.</p>
    </object>
    <script src="o3d-teapot.js"></script>
   </p>
  </body>
</html>