Regex Tester

Test and debug regular expressions online with real-time match highlighting and group capture analysis. Free regex tester for JavaScript regex. No signup required.

Features

Common Use Cases

Regular expressions are essential for input validation, log parsing, data extraction, and find-and-replace operations in code. This tester lets you iterate on a pattern in real time against real test data, so you can verify your regex matches exactly what you intend before embedding it in production code. It is particularly useful for complex patterns like email validation, URL parsing, and log file analysis.

How to Use

  1. Enter your regular expression in the Pattern field. No slashes needed — just the pattern itself.
  2. Set the flags you need: g for global (all matches), i for case-insensitive, m for multiline.
  3. Type or paste your test string. Matches are highlighted in real time as you type.
  4. Inspect captured groups in the Groups panel below the test area.
  5. Copy the final pattern with flags to paste directly into your code.

Privacy & Security

All processing for Regex Tester runs entirely in your browser. Your data — whether text, files, or other content — is never transmitted to any server. DevToolHub has no backend that receives or stores your inputs. This means the tool works even offline once the page has loaded, and there is no risk of your data being intercepted or stored by a third party.

Frequently Asked Questions

What do the flags 'g', 'i', and 'm' mean?

Flags modify the search behavior. 'g' (global) finds all matches. 'i' (case-insensitive) ignores letter casing. 'm' (multiline) allows ^ and $ to match the start/end of a line, not just the whole string.

Why isn't my pattern working?

Check for unescaped special characters — use \. to match a literal dot. The error message below the input box will tell you exactly what is wrong with the syntax.

What regex flavour does this tool use?

This tester uses JavaScript's built-in RegExp engine (ECMAScript regex). It supports character classes, groups, and lookaheads. Patterns tested here will work directly in JavaScript, Node.js, and TypeScript code.

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