Regex

Regex Replace Tester

Preview JavaScript regex replacements locally, including replacement tokens and the number of replacements.

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Uses your browser’s JavaScript RegExp engine. Positions and lengths are zero-based UTF-16 code units; end positions are exclusive. Without g, matching returns only the first match. Sticky y starts at position 0.

Limits: 16,384 pattern code units, 200,000 text code units, 2,000 matches or split parts, and 4,000,000 output code units. User regex execution requires a local worker with a 1,500 ms timeout. Oversized results fail rather than being truncated.

Processed locally in your browser. Inputs and results are not uploaded or saved by this page.

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What does this tool do?

Preview JavaScript regex replacements locally, including replacement tokens and the number of replacements. Code Station Regex tools use the JavaScript regular expression engine. Inputs: Regex Pattern, Test text, Flags, Replacement text. Outputs: Replaced text, Replacement count.

How to use it?

Enter a pattern, test text and replacement text. Select g to replace every match. Choose “Replace text”, then copy individual result values if needed. Clear removes all inputs and results and restores option defaults.