Do custom blocks allow "Overrides" in "Sync Patterns"?

[danielmarif]

I can't see any documentation related to this anywhere. Is there any possible way to make a custom block be overrideable in a sync pattern or the only ones available right now are the core blocks?

[tohidlo]

Hey @danielmarif,
I totally get it – the docs on this are kinda hidden/buried right now. But yes, custom blocks can support overrides in synced patterns (it's not limited to core blocks).
It's an opt-in feature introduced in WP 6.5+. In your block.json, you just need to add support for it like this:

JSON{ "supports": { "pattern": { "overrides": true } }, "attributes": { "content": { // or whatever attribute you want overrideable "type": "string", "source": "html", "selector": "p", "overrides": true } } }

That lets users override specific parts (like text or images) in a synced pattern without breaking the sync for the rest.
The main doc page is here: https://developer.wordpress.org/block-editor/reference-guides/block-api/block-patterns/#overrides

I've done this on a couple custom blocks and it works fine.
Hope that helps! 👍

[danielmarif]

I can't see any "pattern" or "overrides" at block.json in the docs you've sent

[tohidlo]

After double-checking the latest core docs and implementation, pattern overrides in synced patterns are currently only supported on specific core blocks:

Paragraph (content)
Heading (content)
Button (text, url, linkTarget, rel)
Image (url, alt, title)
Custom blocks don't have built-in support for the core/pattern-overrides source yet – there's no opt-in in block.json (like a supports flag) or reliable filter to enable it on custom ones.
The Block Bindings API itself can be extended for other sources (e.g., post meta on custom blocks via filters), but the specific pattern overrides feature is still limited to those core blocks/attributes for now. It's on the roadmap for future expansion (including potential custom block support).
Best reference: https://developer.wordpress.org/news/2024/06/an-introduction-to-overrides-in-synced-patterns
That's why the docs feel sparse on custom blocks – it's just not there yet.
If you're trying to achieve something similar, people sometimes work around it with post meta bindings or other dynamic sources, but for true pattern overrides, core blocks are the only option right now.

[danielmarif]

[tohidlo]

I am not a bot; I use AI to help with correct writing and to check the accuracy of information because English is not my first language, and I might not be able to express myself correctly
I hope I have been able to help, and I wish you success