Santekno/tools
CategoriesTutorials

Regex Tester

Test regular expressions against strings with match highlighting and group extraction.

Processed in your browserUpdated · Jan 2026
Pattern & Test String
Pattern
//g
Test String
0 chars
Matches
Enter a pattern and test string to see matches…
—

How to use Regex Tester

Paste your input on the left, choose the options you want, and the output appears instantly on the right. Everything runs in your browser — none of your data is sent to a server.

  • Paste or type your input in the INPUT panel
  • The output regenerates automatically as you type
  • Use Copy to put the result in your clipboard
  • Click Sample to load a working example

What is Regex Tester?

Regex Tester lets you test JavaScript regular expressions against any input string. It shows all matches with their positions, extracts named and unnamed capture groups, and supports a replace mode. Flags (g, i, m, s, u, y) are fully supported. This tool is part of santekno's developer toolbox — a curated collection of utilities built for engineers who care about speed, privacy, and simplicity.

Common use cases

  • Debugging API payloads and integration issues
  • Inspecting tokens, hashes, or encoded strings during development
  • Generating fixtures and sample data for tests
  • Sharing readable output with teammates in code reviews

FAQ

This tester uses JavaScript (ECMAScript) regex. Note that Go uses a different regex engine (RE2) which does not support lookaheads.