Free Online Tools
19 calculators, decoders, generators, and checkers for everyday security work: score a CVSS vector, plan a subnet, read a certificate or token, build SPF and DMARC records, and check a site's TLS, headers, and DNS. Each tool shows its result first and explains the standard behind it. No account or sign-up needed.
Updated
Certificates and TLS
2 toolsCertificate decoder for PEM, DER, chains, and CSRs. Shows SANs, validity, key size, extensions, and fingerprints, and checks signatures in your browser.
Free SSL checker that reads the certificate chain a server sends and checks trust, the host name, expiry, and which TLS versions it accepts.
DNS and Networks
3 toolsFree DNS lookup for A, AAAA, MX, TXT, NS, SOA, CAA and 10 more record types, with TTLs, DNSSEC status and a three-resolver compare mode.
Free port checker that tests whether one TCP port on your own IP address accepts connections from the internet, with the timeout stated.
Free subnet calculator for IPv4 and IPv6. It shows the network, broadcast, host range and masks, and splits, plans and merges CIDR blocks.
Email Authentication
4 toolsFree DMARC record generator and checker for RFC 9989. Build or paste a record, see every tag explained, and get the records external report services need.
Free email header analyzer that runs in your browser. See every hop in UTC, SPF, DKIM and DMARC results, From alignment, ARC and Microsoft spam fields.
Free SPF record generator and checker. Build or paste a record, count its DNS lookups against the limit of 10, and see every syntax error explained.
Free SPF, DKIM and DMARC checker. It counts SPF DNS lookups, finds the DMARC policy under RFC 9989, and reads DKIM key types and lengths.
Hashes, Passwords and 2FA
5 toolsFree bcrypt generator and checker that hashes and verifies passwords in your browser, warns at 72 bytes, and creates htpasswd lines for Apache and nginx.
Free hash generator for MD5, SHA-1, SHA-256, SHA-512, SHA-3, BLAKE3 and CRC-32 of text or files, with HMAC and a compare field. Runs in your browser.
Free hash identifier that names the format of a hash, validates its structure, and shows its parameters and audit tool modes. Runs in your browser.
Free passphrase generator using the EFF wordlists. It picks random words or characters in your browser and shows the exact entropy of each result in bits.
Free TOTP generator for 2FA codes from a Base32 secret or an otpauth link. Checks a code against nearby time steps and runs in your browser.
Vulnerability Scoring
2 toolsFree CVSS calculator for v3.0, v3.1 and v4.0 vectors. It scores Base, Temporal, Threat and Environmental metrics in your browser.
Free EPSS score lookup for up to 100 CVEs at once: probability, percentile, score date, model version, 30-day history and CISA KEV status.
Web Security
3 toolsFree CSP evaluator that checks a Content-Security-Policy header or meta tag in your browser: fallbacks, unsafe-inline, bypass hosts, nonces and hashes.
JWT decoder that verifies signatures with a secret or public key in your browser. Shows claims, expiry status, and header warnings.
Free security headers checker. Grades HSTS, CSP, frame protection, nosniff, Referrer-Policy and Permissions-Policy, with every redirect and cookie flag.