No. 001 · A developer's toolbox
Small tools.
Running on your machine.
grepyard is a collection of developer tools. Paste a token, inspect a certificate, read the result. Nothing you paste is stored or logged.
JWT decoder
Decode, verify, and encode JSON Web Tokens. All in your browser. Nothing leaves the page.
Regex tester
Test regular expressions against JavaScript, Go (RE2), and Ruby (Oniguruma) engines, with live match highlighting and capture-group inspection.
Base64 / URL / hex
Encode and decode between Base64, URL-percent, and hex. UTF-8 safe round-trips.
Timestamp converter
Convert unix timestamps and ISO 8601 to human-readable times across timezones.
UUID generator
Generate UUID v4 and v7, or decode an existing one to see its version, variant, and timestamp.
Hash calculator
Compute MD5 and SHA-1/256/384/512 of text or files. Runs entirely in your browser, with no uploads.
User-Agent parser
Parse a User-Agent string into browser, OS, device, and engine.
Cron parser
Translate cron expressions into plain English and preview the next five runs.
JSON tools
Format, minify, validate, and query JSON with JSONPath.
X.509 certificate decoder
Inspect subject, issuer, SANs, key usage, validity, and fingerprints from a PEM certificate.
JA4 fingerprint lookup
Look up a JA4 TLS client fingerprint in a corpus we observe ourselves, and see which User-Agents rode which TCP stacks.
Anonymous
No sign-in, no accounts, no tracking cookies. Page counts are anonymous, and nothing here fingerprints you — except one button on the JA4 tool, which says so before you click.
Self-hosted
Analytics, error tracking, metrics, logs, and traces all run on servers we operate. The only third party in the path is Cloudflare, which fronts the site for TLS and DDoS protection.