User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:95.0) Gecko/20100101 Firefox/95.0

Steps to reproduce:

View a page that contains iframes. Demo: https://danielstout5.github.io/Demos/firefox-iframes

This page has one iframe (example.org) directly in the HTML. The other iframe (example.com) is appended via Javascript.

Actual results:

Despite having "Select an iframe as the currently targeted document" checked under developer tool settings, Firefox does not detect the iframes. If I go to the developer tool settings and hover over the disabled button, it says "This button is only available on pages with several iframes"

Expected results:

Firefox should have detected the two iframes and allowed me to select them as the target context.

Chrome handles this correctly - see my attached screenshot from Chrome

Here's a screenshot of the developer tools with that page open - note that the iframe picker button is disabled

The Bugbug bot thinks this bug should belong to the 'Core::DOM: Core & HTML' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Hello dstout,

I think you're hitting a known issue with DevTools + Firefox new site isolation.
You should be able to work around that by either using Firefox Beta (96) and setting devtools.every-frame-target.enabled to true in about:config, or use Firefox Nightly (where the pref is true by default).
We are planning to enable the pref very soon, and hopefully it will be part of Firefox 96 when it reaches release.
Let me know if this wasn't the issue and we'll reopen the bug