Free DMARC tools that run in your browser.
No account, no upload — the work happens in the page, and the only thing that ever leaves it is a domain name sent to a public DNS resolver. Open source, like the rest of the project.
-
DMARC record checker
Look up a domain’s DMARC record and validate every tag — including whether third-party reporting addresses were ever authorized to receive your reports.
-
DMARC record generator
Build a valid DMARC record from a short form, with the defaults left out — plus a plain reading of what it will do to your mail.
-
SPF record checker
Expands every include and counts your DNS lookups against the limit of 10 — the ceiling that breaks SPF with no warning once you cross it.
-
DKIM record checker
Decode a selector’s public key to get its real length, and catch revoked keys and testing mode left switched on. Don’t know your selector? Try the common ones.
-
DMARC report analyzer
Paste or upload an aggregate (RUA) report and get a readable, per-source breakdown. Runs entirely in your browser.
Everything here runs client-side and is open source, like the application itself.
Why there's no server behind these
The three checkers look up DNS directly from your browser over DNS-over-HTTPS, and the generator and report analyzer never make a network request at all — a DMARC record is built from form fields you typed, and a report is XML you already have. There's no backend to send any of it to, which means there's nothing here that could log a domain you looked up or a report you pasted in, by accident or otherwise.
The trade-off is real: a DNS-over-HTTPS resolver still sees the lookup, and very large aggregate reports can make a phone's browser tab slow to parse. For a quick check on a domain you don't control, or a one-off report from a client, that's the right trade. Running the same checks continuously, across a portfolio of domains, is what the self-hosted DMARC Analyzer application is for.