Write and test regular expressions against sample text. View match counts, highlight matched text, extract capture groups, and understand match coordinates instantly in your browser.
Workspace
Use the tool below. Your inputs stay local when the tool supports browser-only processing.
| Match | Index | Length | Captures |
|---|---|---|---|
| No matches found. | |||
Last reviewed: · Testing methodology
Workflow
Type or paste your regex pattern into the pattern field, including any flags like global or case-insensitive. If you are used to a regex tester workflow, you will find the same instant feedback loop here — test your pattern against sample data without setting up a local environment.
Paste one or more sample strings into the test input area that you want to match against your pattern. Like any good regex tester, the tool highlights every match in real time, showing you exactly which portions of your text the regular expression captures.
Examine the highlighted matches and the detailed match info panel to understand capture groups and positions. Iterate on your pattern by editing it directly and watching the results update instantly — just like a dedicated regex tester, this rapid feedback loop helps you get your expression exactly right.
The component constructs a JavaScript RegExp from the pattern and flags, then applies it to the sample text for matches and replacements.
Use short representative text while developing a pattern. Escape literal slashes only when your target syntax requires them.
Test in the actual target runtime when flavor-specific behavior, timeouts, Unicode modes, or production safety matters.
| Option | Best for | Trade-off |
|---|---|---|
| This browser tool | Quick, private, one-off work | Limited by browser memory and the documented feature set |
| Desktop or command-line tool | Batch jobs and repeatable automation | Requires installation and setup |
Reviewed by the Free Online Tools Nest Team on 2026-08-26. The interface, output path, and documented limitations were checked against the current implementation. See our testing methodology for the review process.
Read the testing methodologyWhen you use this regex tester, you get immediate visual feedback on every match, capture group, and replacement operation without running your entire application. It mimics the behavior of a regex tester library call but with a visual interface that shows you exactly what each part of your expression does.
This tester uses the browser's JavaScript RegExp engine and therefore supports ECMAScript syntax and flags. PCRE, Python, .NET, and Java have different features, so test the final pattern again in its actual target runtime.