No. 001 · A developer's toolbox
Small tools.
Running on your machine.
grepyard is a collection of anonymous, client-side developer tools. No sign-in, no accounts, no tracking beyond an anonymous page counter. Paste a token, search a fingerprint, inspect the result — the work happens in your browser.
JWT decoder
Decode, verify, and encode JSON Web Tokens. All in your browser — nothing leaves the page.
JA4 fingerprint lookup
Search the public FoxIO JA4+ database by fingerprint, application, library, device, or OS.
Regex tester
Test JavaScript regular expressions 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. Uses Web Crypto — 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.
Anonymous
No sign-in. No accounts. No cookies beyond your theme. Nothing you paste leaves your browser except the JA4 dataset request, which is a static file we serve ourselves.
Self-hosted
Every dependency — analytics, error tracking, metrics, logs, traces — runs on a server we operate. No third parties get your data.