Regex Tester

Test patterns with highlighted matches and capture groups.

FREE - NO SIGN-UP - RUNS ON YOUR DEVICE

Runs locally in your browser

  • Liveresult
  • 0uploads
  • 1 tapto copy
  • Freeno account
In practice

What you can count on

  • 0uploads
    • Your input stays on this device
    • Nothing is sent for processing
  • Liveoutput
    • Results update in the working area
    • Change inputs and compare instantly
  • 1 tapto copy
    • Copy the result
    • No account or install needed
Specification

Regex Tester at a glance

Input
An expression, flags and test text
Output
Highlighted matches, numbered groups
Method
The browser's own RegExp engine
Capture groups and limits
Named groups; 5000 match cap
Price
Free
Where processing happens
On your device
How to

How to use Regex Tester

  1. 1

    Write the pattern

    Enter your regular expression in the pattern field and add any flags you need beside it.

  2. 2

    Add test text

    Paste the sample text you want to run the pattern against in the third field.

  3. 3

    Read the matches

    Matches are highlighted inside your test text as you type, with capture groups listed underneath — named groups by name. A Copy button sits beside them.

Questions

Frequently asked questions

Does this work without uploading anything?

Yes. The tool processes your input inside the browser tab. Nothing is sent to a processing server or stored in an account.

Can I change the result before copying it?

Yes. Adjust any available control and the result updates. Copy it only when the output matches what you need.

Which browsers are supported?

Current versions of Chrome, Edge, Firefox and Safari support the browser features used here. Very old browsers may lack a required API.

Background

Reading the matches and the groups

Every match is highlighted and each numbered group is listed beneath it. Group 1 is the first opening bracket counting from the left, so nesting changes the numbers.

  • The g flag is added for you, because the panel counts every match rather than stopping at the first one.
  • A pattern that can match nothing matches at every position, which is why the count can exceed the characters.

Full specification

Specification of the Regex Tester tool
InputA JavaScript regular expression, flags and test text.
OutputHighlighted matches and numbered capture groups.
MethodThe browser JavaScript RegExp engine with safe zero-length handling.
Capture groups and limitsA named group is listed by its name, not a number. Highlighting stops at 5000 matches and says so rather than counting further.
PriceFree. Supported by clearly labeled ads outside the working area.
Where processing happensIn your browser tab. Your input is never uploaded.
Next step

Keep going with the same files

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