Developer tools that run in your browser
Regex, cron and JSON utilities that give you the answer and then explain it. No accounts, no uploads, no tab-hopping between four single-purpose sites.
- Nothing you paste leaves your device
- Works properly on a phone
- Free, no sign-up, no nag walls
Start with a tool
Each one works instantly as you type, and each has a reference section underneath explaining what it is actually doing.
- TextRegex Tester
Test a pattern against your text and get a plain-English explanation of what it does.
- DataJSON Formatter and Validator
Prettify, minify and validate JSON — with the exact line and column of any error.
- TimeCron Expression Generator and Parser
Build a schedule visually, or paste one and read it in plain English with the next run times.
- DataJSON to YAML Converter
Convert JSON to YAML and back, with validation in both directions.
Browse by category
Why another set of developer tools?
Your input stays put
Everything runs on your device. Nothing you type is ever uploaded. There is no server to send it to — every tool is JavaScript running in your tab. You can open dev tools and check, or load a tool and pull the network cable.
It explains itself
A regex that matches is not the same as a regex you understand. These tools translate what you wrote back into English, so you can tell whether it does what you meant.
Usable on a phone
Most regex testers are frank about being desktop-only. These are built mobile-first: inputs stack, results sit directly underneath, and nothing shifts as the page loads.
Reference and guides
Written to be read, not to rank. Each one covers something the tool page cannot explain properly on its own.
- Regex Cheat SheetEvery regex token with a worked example, plus where the major languages disagree.
- Cron Cheat SheetField order, special characters, dialect differences and a table of common schedules.
- How to run a cron job every 5 minutesThe correct expression, the common mistake that silently drifts, and every dialect variant.
- Cron syntax compared: standard, Quartz, node-cron and EventBridgeField counts, day-of-week numbering and special characters, and why a copied expression can silently run at the wrong time.
- Regex for email addresses in JavaScriptA pattern worth using, what it deliberately misses, and why chasing RFC 5322 is the wrong goal.
- How to fix JSON parse errorsEach parser message translated into the actual problem, with the fix.
Coming next: JWT decoder, UUID generator, hash generators and Base64/URL encoders — built to the same standard rather than shipped thin. See the about page for how this site is put together and funded.