pct= — gradual rollout percentage

pct= (0-100, default 100) tells receivers to apply the DMARC policy (quarantine or reject) to only that percentage of messages that would otherwise be affected; the rest fall back to the next weaker policy. For example p=reject; pct=25 rejects roughly a quarter of failing mail and lets the other three quarters through, so you can watch for unexpected breakage before committing fully.

pct= has no effect at p=none, since there is no enforcement to apply partially.

Under DMARCbis (RFC 9989), pct= was removed as a defined tag — see deprecated tags for what replaces it. This isn't urgent: a record still publishing pct= keeps working exactly as before, and this tool's health check offers a one-click DNS fix to drop it whenever you're ready.