Developer tools
Everyday utilities for developers: timestamps, regular expressions and more.
Card Number Validator (Luhn)
Check a card number with the Luhn algorithm and detect its network.
Chmod Calculator
Work out Unix file permissions in octal and symbolic form.
CIDR and Subnet Calculator
Calculate network, broadcast and host range from a CIDR block.
Cron Expression Explainer
Explain a cron schedule and see its next run times.
HTTP Status Codes Reference
Look up any HTTP status code by number or keyword.
Regex Tester
Test regular expressions and see every match and capture group.
Unix Timestamp Converter
Convert Unix timestamps to dates and dates to timestamps.
Every Developer tool here is free, needs no sign-up and runs in your browser unless noted on the tool page.