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NotRestoredReasons

files/en-us/web/api/notrestoredreasons/index.md

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{{APIRef("Performance API")}}{{SeeCompatTable}}

The NotRestoredReasons interface of the {{domxref("Performance API", "Performance API", "", "nocode")}} provides report data containing reasons why the current document was blocked from using the back/forward cache ({{Glossary("bfcache")}}) on navigation.

These objects are accessed via the {{domxref("PerformanceNavigationTiming.notRestoredReasons")}} property.

Instance properties

  • {{domxref("NotRestoredReasons.children", "children")}} {{ReadOnlyInline}} {{Experimental_Inline}}
    • : An array of NotRestoredReasons objects, one for each child {{htmlelement("iframe")}} embedded in the current document, which may contain reasons why the top-level frame was blocked relating to the child frames. Each object has the same structure as the parent object — this way, any number of levels of embedded <iframe>s can be represented inside the object recursively. If the frame has no children, the array will be empty; if the document is in a cross-origin <iframe>, children will return null.
  • {{domxref("NotRestoredReasons.id", "id")}} {{ReadOnlyInline}} {{Experimental_Inline}}
    • : A string representing the id attribute value of the <iframe> the document is contained in (for example <iframe id="foo" src="...">). If the document is not in an <iframe> or the <iframe> has no id set, id will return null.
  • {{domxref("NotRestoredReasons.name", "name")}} {{ReadOnlyInline}} {{Experimental_Inline}}
    • : A string representing the name attribute value of the <iframe> the document is contained in (for example <iframe name="bar" src="...">). If the document is not in an <iframe> or the <iframe> has no name set, name will return null.
  • {{domxref("NotRestoredReasons.reasons", "reasons")}} {{ReadOnlyInline}} {{Experimental_Inline}}
    • : An array of {{domxref("NotRestoredReasonDetails")}} objects, each representing a reason why the navigated page was blocked from using the bfcache. If the document is in a cross-origin <iframe>, reasons will return null, but the parent document may show a reason of "masked" if any <iframe>s blocked bfcache usage for the top-level frame.
  • {{domxref("NotRestoredReasons.src", "src")}} {{ReadOnlyInline}} {{Experimental_Inline}}
    • : A string representing the path to the source of the <iframe> the document is contained in (for example <iframe src="exampleframe.html">). If the document is not in an <iframe>, src will return null.
  • {{domxref("NotRestoredReasons.url", "url")}} {{ReadOnlyInline}} {{Experimental_Inline}}
    • : A string representing the URL of the navigated page or <iframe>. If the document is in a cross-origin <iframe>, url will return null.

Instance methods

  • {{domxref("NotRestoredReasons.toJSON", "toJSON()")}} {{Experimental_Inline}}
    • : A {{Glossary("Serialization","serializer")}}; returns a JSON representation of the NotRestoredReasons object.

Examples

See Monitoring bfcache blocking reasons for examples.

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also