<fencedframe>: The Fenced Frame element
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The <fencedframe>
HTML element represents a nested browsing context, embedding another HTML page into the current one. <fencedframe>
s are very similar to <iframe>
elements in form and function, except that:
- Communication is restricted between the
<fencedframe>
content and its embedding site. - A
<fencedframe>
can access cross-site data, but only in a very specific set of controlled circumstances that preserve user privacy. - A
<fencedframe>
cannot be manipulated or have its data accessed via regular scripting (for example reading or setting the source URL).<fencedframe>
content can only be embedded via specific APIs. - A
<fencedframe>
cannot access the embedding context's DOM, nor can the embedding context access the<fencedframe>
's DOM.
The <fencedframe>
element is a type of <iframe>
with more native privacy features built in. It addresses shortcomings of <iframe>
s such as reliance on third-party cookies and other privacy risks. See Fenced frame API for more details.
Attributes
This element includes the global attributes.
allow
Experimental-
Specifies a Permissions Policy for the
<fencedframe>
, which defines what features are available to the<fencedframe>
based on the origin of the request. See Permissions policies available to fenced frames for more details of which features can be controlled via a policy set on a fenced frame. height
Experimental-
A unitless integer representing the height of the fenced frame in CSS pixels. The default is
150
. width
Experimental-
A unitless integer representing the width of the fenced frame in CSS pixels. The default is
300
.
Permissions policies available to fenced frames
Permissions delegated from the top-level context to a fenced frame for allowing and denying features could be used as a communication channel, so constitute a privacy threat. As a result, standard web features that can have their availability controlled via Permissions Policy (for example, camera
or geolocation
) are not available within fenced frames.
The only features that can be enabled by a policy inside fenced frames are the specific features designed to be used inside fenced frames:
- Protected Audience API
attribution-reporting
private-aggregation
shared-storage
shared-storage-select-url
- Shared Storage API
attribution-reporting
private-aggregation
shared-storage
shared-storage-select-url
Currently these are always enabled inside fenced frames. In the future, which ones are enabled will be controllable using the <fencedframe>
allow
attribute. Blocking privacy sandbox features in this manner will also block the fenced frame from loading — there will be no communication channel at all.
Focusing across fenced frame boundaries
The ability of the document's active focus to be moved across fenced frame boundaries (i.e. from an element outside the fenced frame to one inside, or vice versa) is limited. User-initiated actions such as a click or a tab can do so, as there is no fingerprinting risk there.
However, trying to traverse the boundary via an API call such as HTMLElement.focus()
is prohibited — a malicious script could use a series of such calls to leak inferred information across the boundary.
Positioning and scaling
Being a replaced element, the <fencedframe>
allows the position of the embedded document within its box to be adjusted using the object-position
property.
Note: The object-fit
property has no effect on <fencedframe>
elements.
The size of the embedded content may be set by internal contentWidth
and contentHeight
properties of the <fencedframe>
's config
object. In such cases, changing the width
or height
of the <fencedframe>
will change the size of the embedded container on the page, but the document inside the container will be visually scaled to fit. The reported width and height of the embedded document (i.e. Window.innerWidth
and Window.innerHeight
) will be unchanged.
Accessibility
People navigating with assistive technology such as a screen reader can use the title
attribute on an <fencedframe>
to label its content. The title's value should concisely describe the embedded content:
<fencedframe
title="Advertisement for new Log. From Blammo!"
width="640"
height="320"></fencedframe>
Without this title, they have to navigate into the <iframe>
to determine what its embedded content is. This context shift can be confusing and time-consuming, especially for pages with multiple <iframe>
s and/or if embeds contain interactive content like video or audio.
Examples
To set what content will be shown in a <fencedframe>
, a utilizing API (such as Protected Audience or Shared Storage) generates a FencedFrameConfig
object, which is then set as the value of the <fencedframe>
's config
property.
The following example gets a FencedFrameConfig
from a Protected Audience API's ad auction, which is then used to display the winning ad in a <fencedframe>
:
<fencedframe width="640" height="320"></fencedframe>
const frameConfig = await navigator.runAdAuction({
// ...auction configuration
resolveToConfig: true,
});
const frame = document.querySelector("fencedframe");
frame.config = frameConfig;
Technical summary
Content categories | Flow content, phrasing content, embedded content, interactive content, palpable content. |
---|---|
Permitted content | None. |
Tag omission | None, both the starting and ending tag are mandatory. |
Permitted parents | Any element that accepts embedded content. |
Implicit ARIA role | No corresponding role |
Permitted ARIA roles |
application , document ,
img , none ,
presentation
|
DOM interface | HTMLFencedFrameElement |
Specifications
Specification |
---|
Fenced Frame # the-fencedframe-element |
Browser compatibility
BCD tables only load in the browser
See also
- Fenced Frame API
- Fenced frames on developers.google.com
- The Privacy Sandbox on developers.google.com