HeyUtils

HeyUtils is a free collection of 306 developer utilities in 41 categories, grouped under data formats, text and encoding, time and math, API and security, networking and certificates, dev and ops, frontend and mobile, and protocols and AI. Each tool does one job on its own page and opens with an example you can load in one click. The popular ones include a JSON formatter that keeps large integers and decimals exact, a JWT debugger that shows claims as UTC dates and verifies signatures with a key you supply, a Unix timestamp converter, a JavaScript regex tester with visible capture groups, a cron expression builder with run previews, a subnet calculator and a UUID generator covering versions 1 through 7. There's no account or install. Most tools run entirely in the browser, and the network tools say on the page what they send before you run them.