What is a WordPress block’s `save` function’s role and what happens if saved content doesn’t match the current save output?

Question

WordPress Expert — Medium

What is a WordPress block’s `save` function’s role and what happens if saved content doesn’t match the current save output?

Accepted Answer

The `save()` function in WordPress defines the static HTML stored in the database when a post is saved. If the current block version's `save()` output doesn't match the stored markup, WordPress shows a block validation error, making the block invalid and requiring a deprecation record or migration.