RegEx Visualizer is a free browser-based tool for testing, understanding, and debugging regular expressions. It works as a regex visualizer and regex tester online, highlighting matches as you type and showing how different parts of your pattern work.
Enter a regular expression and a test string to see matching results, capture groups, and pattern details. The regular expression tester uses your browser's JavaScript RegExp engine, so you can test patterns without uploading your data to a server.
You can use Test mode for normal pattern matching, Replace mode to preview substitutions, or Diff mode to compare two regex patterns. The tool also includes an explanation view, debugger, presets, cheatsheet, history, and local test cases.
Step 1: Enter Your Regex Pattern
Enter your regular expression and select the flags you need, including g, i, m, s, u, or y.
Step 2: Add Test Text
Paste your sample text into the test area. The regex pattern tester will highlight matching parts and show capture groups.
Step 3: Understand or Debug the Pattern
Open Explanation to see information about individual regex tokens. If you need to investigate a difficult match, use Debug to step through the matching process.
Step 4: Test, Replace, or Compare
Use Replace to preview substitutions, Diff to compare two patterns, or Tests to create your own test cases. When finished, copy your regex pattern together with its flags.
Test Regular Expressions Online
Use the regular expression tester online to check whether a pattern matches your sample text before adding it to a project.
Debug a Regex Pattern
If your expression matches too much or too little, use the debugger and explanation views to understand where the matching behavior differs from what you expected.
Check Form Validation Patterns
Test patterns for emails, usernames, URLs, IDs, slugs, and other input formats with realistic sample data.
Preview Find and Replace
Use Replace mode to see how a replacement string changes your test text before applying similar changes to real data.
Compare Regex Patterns
Use Diff to compare two versions of a pattern when updating or simplifying an existing expression.
Learn Regular Expressions
The visual match highlighting and token explanations make concepts such as capture groups, character classes, and quantifiers easier to understand.
RegEx Visualizer is built around JavaScript regular expressions and supports:
Exploring other developer utilities? Browse all tools including JSON Formatter and XML Formatter.
