DKIM Key Strength Checker
Inspect a DKIM public key, key type and RSA key strength from DNS or a pasted record.
Use a domain + selector for a live DNS lookup, or paste a record to inspect it directly.
Check the strength of a DKIM public key
This tool can look up a DKIM TXT record from a domain and selector or inspect a DKIM record that you paste directly. It reports the key type, RSA bit length where applicable, hash-policy information and service scope.
How to use it
- Enter the sending domain and DKIM selector, or paste a full DKIM public-key record.
- Choose the matching check option.
- Review the key assessment and the raw record.
Why key size matters
Old or undersized RSA keys can weaken a DKIM configuration and may not meet the expectations of modern mail providers. A key-strength check is useful when auditing an existing mail setup or migrating between email services.
RSA and Ed25519
The checker recognizes both RSA-style DKIM keys and Ed25519-style records. Key-size guidance differs by key type, so the assessment is based on the record that is actually present.
Important limitation
A strong public key does not prove that messages are being signed correctly. Full DKIM troubleshooting also requires checking the message signature, selector in use and DNS alignment.