Developer tools, all in one place.
A growing collection of fast, focused developer utilities. No bloat, no accounts, just tools.
3 tools live · More shipping rapidly
Tools
Cron Vision
Visualize any cron expression. See exactly when your job runs — next runs, plain English translation.
Confusion Matrix
Evaluate ML models instantly. Paste predictions and ground truth to see accuracy, precision, recall, F1, and ROC curves.
Regex Tester
Test and debug regular expressions in real time. Match highlighting, capture groups, and flags — all visible at a glance.
JSON Formatter
Paste raw JSON and instantly get it formatted, validated, and syntax-highlighted. Minify or beautify in one click.
SQL Formatter
Format messy SQL queries into clean, readable statements. Supports multiple dialects including PostgreSQL and MySQL.
UUID Generator
Generate cryptographically random UUIDs (v4) in bulk. Copy single or batch output instantly.
Why 404tools
No login
Use any tool instantly. No accounts, no email, no friction.
Open a tool. Use it. Leave. That's how it should work.
No bloat
Every tool does one thing. Nothing more.
No dashboards. No settings panels. No upgrade prompts.
No cost
Free forever. Always.
No freemium. No trial period. No credit card required.