# PatternBench

> Test JavaScript regular expressions locally, inspect matches and captures, preview replacements and check expected cases with a stoppable worker.

A browser-local JavaScript regular-expression workbench with g/i/m/s/u/y flags, optional live evaluation, match highlights, numbered/named captures and exact UTF-16 offsets, syntax explanations, replacement previews, capture extraction, JavaScript code generation and up to 50 expected-match cases. Save and reopen local project JSON files. Each run uses a disposable worker with cancellation and a 1.5-second execution limit.

## Pages

- [PatternBench free browser workbench](https://patternbench.smartfact.ai/app/): Test JavaScript regular expressions locally, inspect matches and captures, preview replacements and check expected cases with a stoppable worker.
- [Free JavaScript Regex Workbench](https://patternbench.smartfact.ai/): Test JavaScript regular expressions locally, inspect matches and captures, preview replacements and check expected cases with a stoppable worker.
- [Your work stays in your browser](https://patternbench.smartfact.ai/privacy/): How PatternBench handles temporary work, copying and downloads.
- [A useful workbench, free to use](https://patternbench.smartfact.ai/about/): What PatternBench does, its limits and its place in SmartFACT.

## Discovery

- [Full text](https://patternbench.smartfact.ai/llms-full.txt)
- [Sitemap](https://patternbench.smartfact.ai/sitemap.xml)