Supported SEO plugins
Metaly reads and writes through whichever SEO plugin is active. You do not configure this and there is nothing to import.
Supported
- Yoast SEO — verified end to end against a live site running Yoast 28.1.
- Rank Math
- All in One SEO
- SEOPress
- No SEO plugin at all. Metaly stores metadata in its own fields and emits the tags itself. Useful mostly as a stepping stone — if you install an SEO plugin later, that plugin takes over rendering.
Alt text is the exception to all of this: it is stored by WordPress itself, so it behaves identically whichever of the above you run. See Image alt text.
Two SEO plugins at once
If more than one is active, Metaly writes through the first it resolves and shows a warning naming the others. That warning is worth reading rather than dismissing: two active SEO plugins is the likeliest explanation for "Metaly wrote it and my page did not change". One plugin holds the value you wrote and a different one renders the tag.
The fix is not in Metaly. Decide which SEO plugin owns your metadata and deactivate the other.
What the connection check proves
Under Settings, the connection check does a full round trip against one post: it writes a probe value, reads it back, requests the rendered page over HTTP and looks for the value in the response, then restores the original.
The third step is the one that matters. A write can persist perfectly and still never reach the page — Yoast, for example, renders from its own indexable table rather than from postmeta, so a correct write with a stale indexable is invisible. Only fetching the page tells you the difference.
Switching SEO plugin mid-run
If you change SEO plugins while a run is in progress, Metaly stops the run rather than applying it. The generated text was written for fields that a different plugin does not read, and writing it anyway would be a run that reports success and changes nothing.