Why use an online regex tester?
Regular expressions are powerful but easy to break. A regex tester helps you iterate faster with immediate match feedback and clear errors.
Common regex tester features
- Live testing against sample text with toggleable flags.
- Match lists with indexes and capture group output.
- Fast copy buttons for results during debugging.
FAQ
Is this regex tester for JavaScript regex?
Yes. It uses JavaScript’s RegExp engine, so syntax and behavior match what you’ll see in JS/TypeScript.
What do the flags mean (g, i, m, s, u, y)?
g=global (all matches), i=case-insensitive, m=multiline, s=dotAll, u=unicode, y=sticky matching.
Why do I get an “Invalid regular expression” error?
Common causes include unescaped special characters, invalid character classes, or unsupported syntax for the JS engine.
Why are there no matches even though the pattern looks correct?
Check flags, whitespace, and whether your pattern needs escaping (for example \d instead of d). Also verify your test text contains the target substring.
Does this upload my text anywhere?
Testing runs in your browser session. If you later add server-side logging/analytics, update this statement accordingly.