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Regex Tester

Inspect JavaScript regex matches and captures in an isolated worker.

JavaScript regex. UTF-16 positions; one-second worker limit.

//gi
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Last reviewed: · Testing methodology

How to use

Inspect JavaScript regex matches and captures in an isolated worker.

1

Enter your input

Pattern up to 2,000 characters; text up to 100,000. Use Try example where available to see the expected shape.

2

Choose options and run

Select the relevant mode or settings. Automatic tools update as you type; other tools use the labeled primary action.

3

Review the result

Check the result against your input, then use the available copy or download action. Edits clear or recompute the result.

Examples and checks

How this tool works

Disposable Web Worker with native JavaScript RegExp. Processing stays in your browser.

Input
Pattern ^; global; text abc
Output
One empty match at index 0

Limits and questions

Inputs are processed in your browser. Analytics and advertising can make separate network requests.

Limits, edge cases, and troubleshooting

One-second timeout, cancellation and at most 500 displayed matches. Indexes use UTF-16. Other regex flavors differ.

When to use another workflow

Use your target editor or runtime when exact platform behavior or a broader capability is required.

Verification

Review record: 2026-08-26. See the documented behavior and limitations above, and the testing standards for the scope of review.

Testing methodology

Frequently asked questions

What does this tool support?
Pattern up to 2,000 characters; text up to 100,000. One-second timeout, cancellation and at most 500 displayed matches. Indexes use UTF-16. Other regex flavors differ.
Where is my input processed?
Tool calculations and conversions run locally in your browser. Existing analytics and advertising requests are separate from input processing.