Preparing the Post Editor for Full iframe Integration

As part of an ongoing effort to modernize the editing experience, WordPress is moving toward running the post editor inside an iframe. This work builds upon the original iframe migration in the template editor and introduces new compatibility measures in WordPress 6.9, ahead of the full transition planned for WordPress 7.0.

For background, see the original post.

What’s Changing in WordPress 6.9

Starting with WordPress 6.9, several important updates have been introduced to prepare for this change, which will be completed in WordPress 7.0.

Browser warnings for legacy blocks

To help developers identify legacy blocks, WordPress 6.9 now displays a browser