SynaPost doesn’t replace your SEO plugin – it writes directly into whichever one you already use, so its analysis and snippet preview keep working exactly as before.
Supported plugins
Each has its own dedicated page linked above covering exactly which fields SynaPost writes into for that plugin.
Auto-detect vs. manual
Under Settings → Content & SEO, the SEO Plugin field defaults to Auto-detect, which picks whichever of the three is active on your site. If you run more than one at once (uncommon, but possible during a migration), you can force a specific plugin instead – the setting shows you which one it currently detects.
If you don’t use one
Choose None (use SynaPost meta only) and SynaPost will still store your focus keyword, meta title, and meta description in its own fields, so nothing is lost if you install an SEO plugin later.