Text tool

Regex Tester

Test JavaScript regular expressions against sample text, inspect matches and debug escaping, flags and multiline behavior.

Tool Workspace

Processing is intended to run locally in your browser whenever possible. Avoid pasting production secrets, access tokens, private keys or sensitive business data into any online tool unless you fully understand the risk.

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Pattern and Test Text

Matches

Core Features

Test JavaScript regular expressions against sample text.
Show matched substrings clearly.
Explain common flag behavior.
Help debug greedy and multiline patterns.

How to Use

Enter a regular expression pattern and flags.
Paste text that represents the real input you need to match.
Run the test and inspect each match.
Adjust escaping, anchors or flags until the match is precise.

Common Errors

Greedy patterns matching too much text.
Forgetting the global flag when expecting multiple matches.
Escaping backslashes differently in strings and regex literals.
Using anchors without understanding multiline behavior.

Real Developer Use Cases

Testing log extraction patterns.
Validating route or slug patterns.
Debugging form validation before shipping a frontend change.

Technical Explanation

Regular expressions are compact but easy to misread. A pattern that works on one example can fail when whitespace, newlines, escaping or repeated matches are involved. A browser-based tester helps developers quickly verify the exact JavaScript regex behavior they will get in application code, including flags and edge cases.