NotRestoredReasons

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

These objects are accessed via the PerformanceNavigationTiming.notRestoredReasons property.

children Read only Experimental

An array of NotRestoredReasons objects, one for each child <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.

id Read only Experimental

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.

name Read only Experimental

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.

reasons Read only Experimental

An array of 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.

src Read only Experimental

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.

url Read only Experimental

A string representing the URL of the navigated page or <iframe>. If the document is in a cross-origin <iframe>, url will return null.

toJSON() Experimental

A serializer; returns a JSON representation of the NotRestoredReasons object.

See Monitoring bfcache blocking reasons for examples.

• Monitoring bfcache blocking reasons
• PerformanceNavigationTiming.notRestoredReasons