Cron Calendar
Explain cron expressions and preview the next run times in any timezone.
OpenTest regex with match highlighting, explanations, and ReDoS risk warnings. - runs entirely in your browser. Free, fast and private.
Enter pattern with flags like g, i, or m.
Paste sample lines the pattern should match.
Groups and capture indices show in real time.
Copy final regex once all test cases pass.
A regex that "works" on one sample and silently fails on the next is worse than no regex. Regex Tester highlights matches live, so you see over-matching and missed groups before the pattern hits production.
Use the playground to tune capture groups, flags, and edge cases against real fixtures from logs or forms. Watch for catastrophic backtracking on hostile input; if a pattern hangs the tab, simplify quantifiers and alternation.
Pitfall: copying a pattern that only works with the /g or /m flag you forgot to enable in code. Match the flags here to the runtime you ship.
Tip: keep a failing case and a passing case in the sample box so refactors do not regress silently.
Sample text stays local to the tester. That matters when fixtures include emails, tokens, or customer IDs you should not paste into public regex sites.
Processes data instantly with no server round-trips.
Your data never leaves your browser. Nothing is uploaded.
Works in any modern browser. Nothing to download or install.
No limits, no sign-up, no credit card required.
Works on desktop, tablet and mobile devices.
Beautiful in both themes. Your preference is saved.
Keyboard shortcut
Adjust groups and flags with instant highlight feedback.
Prove a line parser against messy production-shaped samples.
Spot risky constructs before they land in hot validation paths.
Answers for this tool. For site-wide help, open the FAQ hub.
Regex Tester test regex with match highlighting, explanations, and redos risk warnings. Output stays in your browser for quick iteration.
Prefer redacted samples. Even with local processing, treat prod credentials carefully and rotate anything accidentally shared.
No. Generators and linters produce text for you to copy into Git, CI, or consoles - they do not deploy for you.
Always run official CLIs (kubectl, terraform plan, actionlint, etc.) on the final files after using Regex Tester as a starting point.
Syntax may vary across Kubernetes/Terraform/GitHub Actions versions. Adjust generated snippets to your runtime version.
After the page loads, most authors work offline. Keep a local copy of critical manifests.
Use Sample to learn the format, edit, then Download/Copy into your editor.
Request it via Contact with the platform and version you use.