DKIM Checker

About this DKIM Checker

Our DKIM checker is a fast, free, and clear way to validate a domain’s DKIM setup. Enter your domain and DKIM selector, and the tool performs a complete DKIM lookup—following CNAMEs, parsing tags, and presenting results in the table above. It’s a clean, human-friendly DKIM lookup designed for admins, marketers, and developers who need clear answers promtly.

How to use the checker

1. Type in the domain you want to check.
2. Fill in DKIM selector, or leave blank to auto-try common ones.
3. Click Check DKIM. Results appear in the table below.
4. You can then copy results URL and share it with your team.

What the DKIM validator checks

• DKIM Valid — Yes/No: – Instant pass/fail. It checks for the record presence and syntax.
• Hostname – The exact DNS name queried (e.g., selector._domainkey.example.com).
• Behind CNAME — Yes/No: – It detects whether your key lives behind a CNAME (common with hosted ESPs).
• Key type & length – Surfaces k= (RSA or ed25519) and key length (usually 1024, 2048, 4096).
• Public key – The p= value.
• Fingerprint (SHA-256) – A stable hash of the public key for inventory and rotation tracking.

Why teams prefer this DKIM checker

• Actionable results – clear results table with helpful explanations
• CNAME-aware lookup – follows CNAME chains to where your DKIM TXT actually lives (common with ESP-hosted keys)
• Free and online DKIM validation
• Fast, great UX

What is DKIM?

DKIM (DomainKeys Identified Mail) is an email authentication protocol that lets a sending domain “sign” each message with a cryptographic signature. Receiving mail servers fetch the sender’s public key from DNS at selector._domainkey.your-domain and verify that the signed headers/body weren’t altered and that the sender was authorized to use that domain. DKIM reduces spoofing and phishing, builds sender reputation, and together with SPF and DMARC improves deliverability and compliance with major mailbox providers. If you'd like to read more about DKIM, check out our article on DKIM and its setup (Explained simply).

What is a DKIM selector?

A DKIM selector is a short label (e.g., k1, default, google) placed in the s= tag of the DKIM-Signature header that tells receivers which DNS record to fetch for the public key—specifically selector._domainkey.<your-domain>. Selectors let you run multiple keys at once (by provider, environment, or rollout phase), rotate keys safely without downtime, and migrate services cleanly. For more information, read our article What is a DKIM selector.

Why does DKIM matter?

DKIM proves your domain authorized each email and that it wasn’t altered—cutting spoofing/phishing and improving inbox placement. Providers rely on DKIM for reputation and DMARC alignment, so it’s essential for compliance. When issues arise, a DKIM lookup helps you quickly find CNAME issues, key type, and public key so you can fix deliverability fast.