Debug APIs, patterns, and tokens with 22 developer utilities that run 100 percent locally, so secrets never leave your device. The JSON formatter pretty-prints a 500 KB response and points to exact line-column errors like a missing comma at 1:18. The regex tester highlights matches for digit patterns across sample logs, while the JWT decoder exposes expiry claims instantly. For example, formatting a 10,000-line payload takes a blink, and minifying cuts bytes by roughly 20 percent. Each tool page answers common questions in its FAQ, free and offline.
Popular in Developer Tools: JSON Formatter · Regex Tester · JWT Decoder
Questions? Each tool page has an FAQ — start with the JSON Formatter FAQ. See also our testing methodology.
Reviewed by the Tool4SaaS Editorial Team · Authors · How we test
In practice, they are 22 free developer utilities that run 100 percent locally so secrets never leave your device. The JSON Formatter pretty-prints a 500 KB response and flags a missing comma at 1:18, while Regex Tester highlights digit matches across logs. Most work offline after first load.
Start debugging with JSON Formatter, Regex Tester, and JWT Decoder for everyday code chores. Format a 10,000-line payload in a blink, test digit patterns against sample logs, then decode expiry claims instantly. Each page includes a 4-step guide and minification that cuts bytes by roughly 20 percent.
Yes — every developer tool is free with no signup and no upload, running 100 percent in your browser. JWT Decoder exposes expiry claims locally, so tokens stay private on your device. Only live fetches need internet, clearly labeled. You can safely paste a 500 KB JSON sample or 10,000 lines.
Cache the page JSON Formatter once while online and keep the tab open afterward. Most developer tools then validate locally without internet, catching a missing comma at 1:18 or minifying by 20 percent offline. Closing the tab wipes pasted secrets. No install or account is ever needed.
Dive into each tool FAQ for syntax edge cases — open JSON Formatter FAQ for fixing a missing comma at 1:18 in 500 KB files. You will find regex digit examples and JWT expiry checks and 10,000-line performance notes. See our testing methodology and contact page for tool requests.