HTML

Living Standard — Last Updated 22 November 2022

1. 1. 1. 4.8.5 iframe要素
      2. 4.8.6 embed要素
      3. 4.8.7 object要素

4.8.5 iframe要素

カテゴリー：

フローコンテンツ。

フレージングコンテンツ。

エンベディッドコンテンツ。

インタラクティブコンテンツ。

パルパブルコンテンツ。

この要素を使用できるコンテキスト：

エンベディッドコンテンツが期待される場所。

コンテンツモデル：

Nothing。

text/htmlにおけるタグ省略：

どちらのタグも省略不可。

コンテンツ属性：

グローバル属性

src — リソースのアドレス

srcdoc — iframe内でレンダリングする文書

name — Name of nested navigable

sandbox — ネストされたコンテンツのセキュリティルール

allow — iframeのコンテンツに適用されるパーミッションポリシー

allowfullscreen — iframeのコンテンツにrequestFullscreen()の使用を許可するかどうか

width — 横の次元

height — 縦の次元

referrerpolicy — 要素によって開始されたフェッチのためのリファラーポリシー

loading — 読み込み延期を決定するときに使用

アクセシビリティの考慮：

著者向け。

実装者向け。

DOMインターフェイス：

[Exposed=Window]
interface HTMLIFrameElement : HTMLElement {
  [HTMLConstructor] constructor();

  [CEReactions] attribute USVString src;
  [CEReactions] attribute DOMString srcdoc;
  [CEReactions] attribute DOMString name;
  [SameObject, PutForwards=value] readonly attribute DOMTokenList sandbox;
  [CEReactions] attribute DOMString allow;
  [CEReactions] attribute boolean allowFullscreen;
  [CEReactions] attribute DOMString width;
  [CEReactions] attribute DOMString height;
  [CEReactions] attribute DOMString referrerPolicy;
  [CEReactions] attribute DOMString loading;
  readonly attribute Document? contentDocument;
  readonly attribute WindowProxy? contentWindow;
  Document? getSVGDocument();

  // also has obsolete members
};

The iframe element represents its nested navigable.

The src attribute gives the URL of a page that the element's nested navigable is to contain. 属性が存在する場合、潜在的にスペースで囲まれた妥当な空でないURLでなければならない。itemprop属性がiframe要素で指定される場合、srcも指定されなければならない。

The srcdoc attribute gives the content of the page that the element's nested navigable is to contain. 属性の値は、iframe srcdoc文書のソースである。

srcdoc属性が存在する場合、指定された順序で、次の構文上のコンポーネントを構成するHTML構文を使用した値を持たなければならない：

1. 任意の数のコメントおよびASCII空白文字。
2. 任意で、DOCTYPE。
3. 任意の数のコメントおよびASCII空白文字。
4. html要素の形式で、文書要素。
5. 任意の数のコメントおよびASCII空白文字。

上記の要件は、同様にXML文書で当てはまる。

<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 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 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 sandbox srcdoc="<p>hey that's earl's table.
<p>you should get earl&amp;amp;me on the next cover."></iframe>
 </article>

HTML構文において、著者は属性の内容を包むためにU+0022 QUOTATION MARK文字（"）を使用することを単に覚えておく必要があり、それからすべてのU+0026 AMPERSAND（&）およびU+0022 QUOTATION MARK（"）文字をエスケープし、そしてsandbox属性を指定し、コンテンツの安全な埋め込みを確実にする必要がある。（さらに"ではなく"になるよう、引用符を確実にするために、引用符の前にアンパサンドをエスケープすることを忘れないこと。）

XMLでU+003C LESS-THAN SIGN（<）文字も同様にエスケープする必要がある。属性値正規化を防ぐために、一部のXMLの空白文字―具体的にはU+0009 CHARACTER TABULATION（tab）、U+000A LINE FEED（LF）、U+000D CARRIAGE RETURN（CR）―もまたエスケープする必要がある。[XML]

src属性とsrcdoc属性が両方ともに指定される場合、srcdoc属性が優先される。これは、著者にsrcdoc属性をサポートしないレガシーユーザーエージェントに対してフォールバックURLを提供できる。

When an iframe element element is inserted into a document whose browsing context is non-null, the user agent must run these steps:

1. Create a new nested navigable for element.

2. If element has a sandbox attribute, then parse the sandboxing directive given the attribute's value and element's iframe sandboxing flag set.

3. Process the iframe attributes for element, with initialInsertion set to true.

When an iframe element is removed from a document, the user agent must destroy the nested navigable of the element.

This happens without any unload events firing (the element's nested navigable and its Document are destroyed, not unloaded).

Whenever an iframe element with a non-null nested navigable has its srcdoc attribute set, changed, or removed, the user agent must process the iframe attributes.

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

To process the iframe attributes for an element element, with an optional boolean initialInsertion (default false):

1. If element's srcdoc attribute is specified, then:

   1. Set element's current navigation was lazy loaded boolean to false.

   2. If the will lazy load element steps given element return true, then:

      1. Set element's lazy load resumption steps to the rest of this algorithm starting with the step labeled navigate to the srcdoc resource.

      2. Set element's current navigation was lazy loaded boolean to true.

      3. Start intersection-observing a lazy loading element for element.

      4. Return.

   3. Navigate to the srcdoc resource: navigate an iframe or frame given element, about:srcdoc, the empty string, and the value of element's srcdoc attribute.

      The resulting Document must be considered an iframe srcdoc document.

2. Otherwise:

   1. Let url be the result of running the shared attribute processing steps for iframe and frame elements given element and initialInsertion.

   2. If url is null, then return.

   3. If url matches about:blank and initialInsertion is true, then:

      1. Run the iframe load event steps given element.

      2. Return.

   4. Let referrerPolicy be the current state of element's referrerpolicy content attribute.

   5. Set element's current navigation was lazy loaded boolean to false.

   6. If the will lazy load element steps given element return true, then:

      1. Set element's lazy load resumption steps to the rest of this algorithm starting with the step labeled navigate.

      2. Set element's current navigation was lazy loaded boolean to true.

      3. Start intersection-observing a lazy loading element for element.

      4. Return.

   7. Navigate: navigate an iframe or frame given element, url, and referrerPolicy.

The shared attribute processing steps for iframe and frame elements, given an element element and a boolean initialInsertion, are:

1. Let url be the URL record about:blank.

2. If element has a src attribute specified, and its value is not the empty string, then parse the value of that attribute relative to element's node document. If this is successful, then set url to the resulting URL record.

3. If the inclusive ancestor navigables of element's node navigable contains a navigable whose active document's URL equals url with exclude fragments set to true, then return null.

4. If url matches about:blank and initialInsertion is true, then perform the URL and history update steps given element's nested navigable's active document and url.

   This is necessary in case url is something like about:blank?foo. If url is just plain about:blank, this will do nothing.

5. Return url.

To navigate an iframe or frame given an element element, a URL url, a referrer policy referrerPolicy, and an optional string-or-null srcdocString (default null):

1. Let historyHandling be "push".

2. If element's nested navigable's active document is not completely loaded, then set historyHandling to "replace".

3. Navigate element's nested navigable to url using element's node document, with historyHandling set to historyHandling, referrerPolicy set to referrerPolicy, and documentResource set to scrdocString.

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.

To run the iframe load event steps, given an iframe element element:

1. Assert: element's nested navigable is not null.

2. Let childDocument be element's nested navigable's active document.

3. If childDocument has its mute iframe load flag set, then return.

4. Set childDocument's iframe load in progress flag.

5. Fire an event named load at element.

6. Unset childDocument'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.

If an element type potentially delays the load event, then for each element element of that type, the user agent must delay the load event of element's node document if element's nested navigable is non-null and any of the following are true:

• element's nested navigable's active document is not ready for post-load tasks.

• element's nested navigable's is delaying load events is true.

• Anything is delaying the load event of element's nested navigable's active document.

If, during the handling of the load event, element's nested navigable is again navigated, that will further delay the load event.

Each iframe element has an associated current navigation was lazy loaded boolean, initially false. It is set and unset in the process the iframe attributes algorithm.

An iframe element whose current navigation was lazy loaded boolean is false potentially delays 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 parsed, the nested navigable will remain at the initial about:blank Document.

If the user navigates away from this page, the iframe's nested navigable's active 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 navigable target name. The given value is used to name the element's nested navigable if present when that is created.

sandbox属性が指定された場合、iframeによってホストされるあらゆるコンテンツに一連の追加の制限が可能になる。その値は、ASCII大文字・小文字不区別である順不同の一意な空白区切りトークンの集合でなければならない。許可される値は次のとおり：

• allow-downloads
• allow-forms
• allow-modals
• allow-orientation-lock
• allow-pointer-lock
• allow-popups
• allow-popups-to-escape-sandbox
• allow-presentation
• allow-same-origin
• allow-scripts
• allow-top-navigation
• allow-top-navigation-by-user-activation
• allow-top-navigation-to-custom-protocols

When the attribute is set, the content is treated as being from a unique origin, forms, scripts, and various potentially annoying APIs are disabled, and links are prevented from targeting other navigables. 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 traversable navigable; the allow-top-navigation-by-user-activation keyword behaves similarly but allows such navigation only when the browsing context's active window has transient activation; the allow-top-navigation-to-custom-protocols reenables navigations toward non fetch scheme to be handed off to external software; and the allow-forms, allow-modals, allow-orientation-lock, allow-pointer-lock, allow-popups, allow-presentation, allow-scripts, and allow-popups-to-escape-sandbox keywords re-enable forms, modal dialogs, screen orientation lock, the pointer lock API, popups, the presentation API, scripts, and the creation of unsandboxed auxiliary browsing contexts respectively. allow-downloadsキーワードは、コンテンツでダウンロードを実行可能にする。[POINTERLOCK] [SCREENORIENTATION] [PRESENTATION]

allow-top-navigationおよびallow-top-navigation-by-user-activationキーワードは、重複するため、両方指定されてはならない。そのような不適合マークアップにおいて、allow-top-navigationのみが効果を持つ。

同様に、allow-top-navigationまたはallow-popupsのいずれかが指定されている場合、allow-top-navigation-to-custom-protocolsキーワードを指定てはならない。これは冗長となるためである。

サンドボックス化されたコンテンツの内部でalert()、confirm()、およびprompt()を許可するためには、allow-modalsキーワードとallow-same-originキーワードの両方を指定する必要があり、かつロードされるURLはトップレベルの生成元と同一生成元である必要がある 。allow-same-originキーワードなしで、コンテンツは異なる生成元として扱われ、異なる生成元のコンテンツは単純なダイアログを表示できない。

効果的に完全にサンドボックスを破壊する、iframeを含むページが埋め込まれたページに簡単にsandbox属性を削除して再読み込みできるので、埋め込まれたページが同一生成元を持つときに、allow-scriptsおよびallow-same-originの両方のキーワードを共に設定する。

These flags only take effect when the nested navigable of the iframe element is navigated. それらを削除する、または全体のsandbox属性を削除することは、すでに読み込まれたページに影響を与えない。

潜在的に敵対的なファイルは、iframe要素を含むファイルと同じサーバーから提供されるべきではない。攻撃者がiframe内よりむしろ、直接敵対コンテンツを単に訪問することをユーザーに納得させることができる場合、敵対コンテンツをサンドボックス化することは、最小限の助けとなる。敵対的なHTMLコンテンツが原因で発生する可能性のある損害を制限するために、それは独立した専用ドメインから提供されるべきである。たとえsandbox属性の保護なしで、ユーザーが騙されて直接そのページを訪れたとしても、別のドメインを使用することは、ファイル内のスクリプトがサイトを攻撃できないことを保証する。

When an iframe element's sandbox attribute is set or changed while it has a non-null nested navigable, the user agent must parse the sandboxing directive given the attribute's value and the iframe element's iframe sandboxing flag set.

When an iframe element's sandbox attribute is removed while it has a non-null nested navigable, the user agent must empty the iframe element's iframe sandboxing flag set.

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

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

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

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

<a href=D>Link</a>

The allow attribute, when specified, determines the container policy that will be used when the permissions policy for a Document in the iframe's nested navigable is initialized. その値はシリアライズされたパーミッションポリシーでなければならない。[PERMISSIONSPOLICY]

<iframe src="https://maps.example.com/" allow="geolocation"></iframe>

allowfullscreen属性は、真偽属性である。When specified, it indicates that Document objects in the iframe element's nested navigable will be initialized with a permissions policy which allows the "fullscreen" feature to be used from any origin. これは、パーミッションポリシー属性を処理するアルゴリズムによって実施される。[PERMISSIONSPOLICY]

<article>
 <header>
  <p><img src="/usericons/1627591962735"> <b>Fred Flintstone</b></p>
  <p><a href="/posts/3095182851" rel=bookmark>12:44</a> — <a href="#acl-3095182851">Private Post</a></p>
 </header>
 <p>Check out my new ride!</p>
 <iframe src="https://video.example.com/embed?id=92469812" allowfullscreen></iframe>
</article>

Neither allow nor allowfullscreen can grant access to a feature in an iframe element's nested navigable if the element's node document is not already allowed to use that feature.

To determine whether a Document object document is allowed to use the policy-controlled-feature feature, run these steps:

1. If document's browsing context is null, then return false.

2. If document is not fully active, then return false.

3. If the result of running is feature enabled in document for origin on feature, document, and document's origin is "Enabled", then return true.

4. falseを返す。

Because they only influence the permissions policy of the nested navigable's active document, the allow and allowfullscreen attributes only take effect when the nested navigable of the iframe is navigated. それらを追加または削除しても、すでに読み込まれている文書には影響しない。

iframe要素は、埋め込まれたコンテンツが特定のサイズをもつ（たとえば単位が明確に定義された次元をもつ）場合、次元属性をサポートする。

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

referrerpolicy属性は、リファラーポリシー属性である。その目的は、iframe属性を処理するときに使用されるリファラーポリシーを設定することにある。[REFERRERPOLICY]

loading属性は、遅延読み込み属性である。その目的は、ビューポート外にあるiframeを読み込むためのポリシーを示すことである。

When the loading attribute's state is changed to the Eager state, the user agent must run these steps:

1. Let resumptionSteps be the iframe element's lazy load resumption steps.

2. If resumptionSteps is null, then return.

3. Set the iframe's lazy load resumption steps to null.

4. Invoke resumptionSteps.

iframe要素の子孫は何も表さない。（iframe要素をサポートしないレガシーユーザーエージェントにおいて、コンテンツはフォールバックコンテンツとして機能することができるマークアップとして解析される。）

HTMLパーサーは、テキストとしてiframe要素の内側のマークアップを扱う。

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

The supported tokens for sandbox's DOMTokenList are the allowed values defined in the sandbox attribute and supported by the user agent.

The allowFullscreen IDL attribute must reflect the allowfullscreen content attribute.

The referrerPolicy IDL attribute must reflect the referrerpolicy content attribute, limited to only known values.

The loading IDL attribute must reflect the loading content attribute, limited to only known values.

The contentDocument getter steps are to return the this's content document.

The contentWindow getter steps are to return this's content window.

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

4.8.6 embed要素

カテゴリー：

フローコンテンツ。

フレージングコンテンツ。

エンベディッドコンテンツ。

インタラクティブコンテンツ。

パルパブルコンテンツ。

この要素を使用できるコンテキスト：

エンベディッドコンテンツが期待される場所。

コンテンツモデル：

Nothing。

text/htmlにおけるタグ省略：

終了タグなし。

コンテンツ属性：

グローバル属性

src — リソースのアドレス

type — 埋め込みリソースタイプ

width — 横の次元

height — 縦の次元

名前空間を持たないその他の属性（文参照）。

アクセシビリティの考慮：

著者向け。

実装者向け。

DOMインターフェイス：

[Exposed=Window]
interface HTMLEmbedElement : HTMLElement {
  [HTMLConstructor] constructor();

  [CEReactions] attribute USVString src;
  [CEReactions] attribute DOMString type;
  [CEReactions] attribute DOMString width;
  [CEReactions] attribute DOMString height;
  Document? getSVGDocument();

  // also has obsolete members
};

The embed element provides an integration point for an external application or interactive content.

src属性は、埋め込まれているリソースのURLを与える。属性が存在する場合、潜在的にスペースで囲まれた妥当な空でないURLを含まなければならない。

itempropがembed要素で指定される場合、src属性も指定されなければならない。

type属性が存在する場合は、インスタンスを生成するプラグインが選択されるMIMEタイプを提供する。値は妥当なMIMEタイプ文字列でなければならない。type属性とsrc属性の両方が存在する場合、type属性は、src属性で指定されたリソースの明示的なContent-Typeメタデータと同じ型を指定しなければならない。

While any of the following conditions are occurring, any plugin instantiated for the element must be removed, and the embed element represents nothing:

• The element has neither a src attribute nor a type attribute.

• The element has a media element ancestor.

• The element has an ancestor object element that is not showing its fallback content.

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

• The element is in a document or was in a document the last time the event loop reached step 1.
• The element's node document is fully active.
• The element has either a src attribute set or a type attribute set (or both).
• The element's src attribute is either absent or its value is not the empty string.
• The element is not a descendant of a media element.
• The element is not a descendant of an object element that is not showing its fallback content.
• The element is being rendered, or was being rendered the last time the event loop reached step 1.

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 an element task on the embed task source given the element to run the embed element setup steps for that element.

The embed element setup steps for a given embed element element are as follows:

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

2. If element has a src attribute set, then:

   1. Let url be the result of parsing the value of element's src attribute, relative to element's node document.

   2. If url is failure, then return.

   3. Let request be a new request whose URL is url, client is element's node document's relevant settings object, destination is "embed", credentials mode is "include", mode is "navigate", initiator type is "embed", and whose use-URL-credentials flag is set.

   4. Fetch request, with processResponse set to the following steps given response response:

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

      2. If response is a network error, then fire an event named load at element, and return.

      3. Let type be the result of determining the type of content given element and response.

      4. Switch on type:

         null

         1. Display no plugin for element.

         そうでなければ

         1. If element's nested navigable is null, then create a new nested navigable for element.

         2. Navigate element's nested navigable to response's URL using element's node document, with response set to response, and historyHandling set to "replace".

            element's src attribute does not get updated if the nested navigable gets further navigated to other locations.

         3. element now represents its nested navigable.

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

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

3. Otherwise, display no plugin for element.

To determine the type of the content given an embed element element and a response response, run the following steps:

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

2. If the path component of response's url matches a pattern that a plugin supports, then return the type that that plugin can handle.

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

3. If response has explicit Content-Type metadata, and that value is a type that a plugin supports, then return that value.

4. Return null.

It is intentional that the above algorithm allows response to have a non-ok status. 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).

To display no plugin for an embed element element:

1. Destroy the nested navigable of element.

2. Display an indication that no plugin could be found for element, as the contents of element.

3. element now represents nothing.

The embed element has no fallback content; its descendants are ignored.

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

The embed element potentially delays the load event.

embed要素は、次元属性をサポートする。

IDL属性src、およびtypeのそれぞれは、同じ名前の各コンテンツ属性を反映しなければならない。

4.8.7 object要素

カテゴリー：

フローコンテンツ。

フレージングコンテンツ。

エンベディッドコンテンツ。

記載 フォームに関連付けられた要素。

パルパブルコンテンツ。

この要素を使用できるコンテキスト：

エンベディッドコンテンツが期待される場所。

コンテンツモデル：

透過的。

text/htmlにおけるタグ省略：

どちらのタグも省略不可。

コンテンツ属性：

グローバル属性

data — リソースのアドレス

type — 埋め込みリソースタイプ

name — Name of nested navigable

form — form要素とこの要素を関連付ける

width — 横の次元

height — 縦の次元

アクセシビリティの考慮：

著者向け。

実装者向け。

DOMインターフェイス：

[Exposed=Window]
interface HTMLObjectElement : HTMLElement {
  [HTMLConstructor] constructor();

  [CEReactions] attribute USVString data;
  [CEReactions] attribute DOMString type;
  [CEReactions] attribute DOMString name;
  readonly attribute HTMLFormElement? form;
  [CEReactions] attribute DOMString width;
  [CEReactions] attribute DOMString height;
  readonly attribute Document? contentDocument;
  readonly attribute WindowProxy? contentWindow;
  Document? getSVGDocument();

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

  // 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 or as a nested navigable.

data属性は、リソースのURLを指定する。これは存在しなければならず、かつ潜在的にスペースで囲まれた妥当な空でないURLを含まなければならない。

type属性が存在する場合、リソースのタイプを指定する。存在する場合、属性は妥当なMIMEタイプ文字列でなければならない。

The name attribute, if present, must be a valid navigable target name. The given value is used to name the element's nested navigable, if applicable, and if present when the element's nested navigable is created.

Whenever one of the following conditions occur:

• the element is created,
• the element is popped off the stack of open elements of an HTML parser or XML parser,
• the element is not on the stack of open elements of an HTML parser or XML parser, and it is either inserted into a document or removed from a document,
• the element's node document changes whether it is fully active,
• one of the element's ancestor object elements changes to or from showing its fallback content,
• the element's classid attribute is set, changed, or removed,
• the element's classid attribute is not present, and its data attribute is set, changed, or removed,
• neither the element's classid attribute nor its data attribute are present, and its type attribute is set, changed, or removed,
• the element changes from being rendered to not being rendered, or vice versa,

...the user agent must queue an element task on the DOM manipulation task source given the object element 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 node 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 whose browsing context is non-null, or if the element's node 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 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, then the user agent may jump to the step below labeled fallback without fetching the content to examine its real type.

   2. Parse a URL given the data attribute, relative to the element's node document.

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

   4. Let request be a new request whose URL is the resulting URL record, client is the element's node document's relevant settings object, destination is "object", credentials mode is "include", mode is "navigate", initiator type is "object", and whose use-URL-credentials flag is set.

   5. Fetch request.

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

   6. 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.

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

   8. Determine the resource type, as follows:

      1. Let the resource type be unknown.

      2. 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 type, but the remote site overrides that and instead furnishes the user agent with a resource that triggers a different type of content with different security characteristics.

      3. 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 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 computed 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.

      4. If applying the URL parser algorithm to the URL of the specified resource (after any redirects) results in a URL record 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.

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

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

      If the object element's nested navigable is null, then create a new nested navigable for the element.

      Let response be the response from fetch.

      If response's URL does not match about:blank, then navigate the element's nested navigable to response's URL using the element's node document, with historyHandling set to "replace".

      The data attribute of the object element doesn't get updated if the nested navigable gets further navigated to other locations.

      The object element represents its nested navigable.

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

      Destroy the nested navigable of the object element.

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

      The object element represents the specified image.

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

      そうでなければ

      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.

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

   11. If the object element does not represent its nested navigable, then once the resource is completely loaded, queue an element task on the DOM manipulation task source given the object element to fire an event named load at the element.

       If the element does represent its nested navigable, then an analogous task will be queued when the created Document is completely finished loading.

   12. Return.

4. Fallback: The object element represents the element's children. This is the element's fallback content. Destroy the nested navigable for the element.

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.

The object element potentially delays the load event.

form属性は、明示的にそのフォームの所有者とobject要素を関連付けるために使用される。

object要素は次元属性をサポートする。

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

The contentDocument getter steps are to return this's content document.

The contentWindow getter steps are to return this's content window.

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.

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