A block validation warning means its saved markup differs from what the current block expects. Preserve the content before attempting conversion.
Steps
- Copy the affected block’s content or retain a revision of the item before making changes. Note any recent manual HTML edit or plugin/theme change.
- Use the block’s recovery option when offered, then compare text, links, attributes, and layout. Automatic recovery can remove code that the block does not recognize.
- If Resolve is available, compare its current and converted representations. Choose deliberately between keeping HTML and converting to the expected blocks.
- For intentional custom markup, an HTML or Classic block may preserve the content with a different editing experience. Test this on a copy before replacing the original block.
- If many blocks break after a component change, check that component’s compatibility and test recovery in staging rather than converting the entire site in bulk.
Check the result
Save, reopen the editor, and inspect the published result. Confirm that the warning is gone and that no needed content or behavior disappeared.
Before you continue
Deleting the whole post is unnecessary for one invalid block. Do not accept a conversion solely because the warning vanishes; review what the conversion changed.
Documentation for this guidance: wordpress.org — block error unexpected or invalid content.
