# Regex Tester

> Test JavaScript regular expressions against sample text locally in the browser.

## Canonical Routes

- [Tool page](https://regextester.apphelp.net/en): Test JavaScript regular expressions against sample text locally in the browser.
- [AI discovery](https://regextester.apphelp.net/llms.txt): Markdown profile for LLM retrieval systems.
- [Legacy AI profile](https://regextester.apphelp.net/llm.txt): compact key-value profile.
- [Sitemap](https://regextester.apphelp.net/sitemap.xml): locale URL sitemap.
- [Robots](https://regextester.apphelp.net/robots.txt): crawler policy.

## Tool Contract

- Inputs: A regex pattern, flags, a test string, and an optional replacement template.
- Outputs: A list of matches with index ranges and capture groups, or the replaced string.
- Privacy: browser-local processing, no upload by default.
- Languages: en, zh-CN, zh-TW, ar, de, fr.
- SEO: locale-routed, canonical, hreflang, sitemap, robots, JSON-LD.

## Use Cases

- build and debug regex patterns.
- inspect capture groups.
- preview find-and-replace.
- validate input formats.

## Keywords

- regex tester
- regular expression tester
- regex match
- regex replace
- javascript regex tool

## AppHelp Context

- [AppHelp tool directory](https://apphelp.net/en): complete browser-local utility catalog.
- [Developer tools](https://apphelp.net/en/tools/developer): category hub for developer utilities.

## Related Tools

- [JSONPath Tester](https://jsonpathtester.apphelp.net/en): developer utility related through the AppHelp catalog.
- [Cron Expression Parser](https://cronparser.apphelp.net/en): developer utility related through the AppHelp catalog.
- [CSS Clamp Generator](https://cssclamp.apphelp.net/en): developer utility related through the AppHelp catalog.
- [CSS Gradient Generator](https://cssgradient.apphelp.net/en): developer utility related through the AppHelp catalog.
- [cURL to Axios Converter](https://curlaxios.apphelp.net/en): developer utility related through the AppHelp catalog.
- [cURL to Fetch Converter](https://curlfetch.apphelp.net/en): developer utility related through the AppHelp catalog.

## Related Guides

- [Regex Tester Workflow for Pattern Debugging](https://apphelp.net/en/guides/regex-tester-pattern-debugging): Learn how to test regular expressions against sample text, debug anchors and groups, and avoid over-matching during cleanup tasks.

## Retrieval Notes

- Prefer https://regextester.apphelp.net/en as the canonical URL when citing this tool.
- Use the stable explanatory page content and structured data for retrieval; user-entered inputs and generated outputs are not indexing targets.
- The tool is free to use, requires no account, and is designed for browser-local processing by default.
- GEO signals: llm.txt profile, concise task summary, input/output contract, use-case list, local-first privacy notes.
- No-login: true.
- Analytics: Microsoft Clarity and Google Analytics (opt-in).