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All toolsNetworkSSL certificate checker

SSL certificate checker

Inspect a server's TLS certificate: issuer, SANs, expiry, key, protocol and cipher.

SSL certificate checker options
Runs in the background · stops after 40s
Results appear hereFill in the form and press Run.

More network tools

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DNS lookup

Query A, AAAA, MX, TXT, NS, SOA, CAA and more through public resolvers, with TTLs.

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Email DNS checker

Check a domain's MX, SPF, DMARC, DKIM, MTA-STS and BIMI setup, with a pass/fail verdict per record.

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HTTP headers & redirects

Follow a URL's redirect chain and inspect status codes, response headers and security headers.

Open tool

WHOIS / RDAP lookup

Registration data for a domain or IP from RDAP: registrar, dates, status, name servers, network owner.

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Fibonacci ToolBox

Fibonacci ToolBox gathers the small utilities every team reaches for, runs them safely in the background, and forgets your files a few hours later.

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Fibonacci ToolBox is a product of Fibonacci Impact LLC.