Cheap Utilities

WCAG contrast ratio between two hex colors with AA and AAA pass/fail for normal and large text.

Explain a 5-field cron expression in plain English and list the next 5 run times in UTC.

Check email address syntax, role accounts (info@, admin@) and known throwaway domains. No DNS lookup, nothing sent.

SHA-256, SHA-1, SHA-512 and MD5 digests of a short text in hex and base64, with byte length and base64 encoding.

Classify an IPv4 or IPv6 address: public, private, loopback, link-local, CGNAT or reserved, plus reverse-DNS name.

Structural diff of two JSON documents: added, removed, changed and type-changed paths, arrays compared by index.

Repair broken JSON: trailing commas, single quotes, bare keys, comments, Python None/True, missing brackets. Returns parsed.

Compare two semver versions by precedence and test whether a version satisfies a range like ^1.2.0 or >=2 <3.

Text statistics for English: words, sentences, reading time and Flesch reading ease with a difficulty verdict.

Convert a unix timestamp or ISO time to ISO, local time in any IANA zone, weekday, ISO week and relative time.

Normalize a URL: lowercase host, default port and fragment removed, sorted query, tracking parameters stripped.

Inspect a UUID: valid or not, version (1-8), variant, and the embedded timestamp for v1, v6 and v7 UUIDs.