Regex Tester
Use Regex Tester to test regular expressions — free, immediate, and with nothing to install. Parsing, formatting and validation all run in your browser, so API keys, tokens and internal payloads are never transmitted. It is used most by frontend developers checking a token or payload shape. Handles large payloads — several megabytes of JSON is fine. Free, unlimited, and free of the upsells most tools of this kind carry.
Key features
- Handles large payloads — several megabytes of JSON is fine.
- Nothing is logged, which is what makes it safe for production data.
- Works on desktop, tablet and phone — no separate app to install.
- No ads interrupting the tool itself, and no upsell before the result.
How to use Regex Tester
- Paste your input: Drop the payload, code or value into the box above.
- Run it: Press the action button — errors are reported with their position.
- Take the output: Copy the result, or download it when the output is a file.
Frequently asked questions
- Does it follow the official spec? — Yes — the published specification, not a simplified version, so results match your language's own parser.
- Is there a rate limit? — None. There is no server involved, so nothing to limit.
- What happens with invalid input? — You get the position of the problem rather than a blank failure, so it is usable as a validator.
- How large an input can it take? — Several megabytes is routine. The limit is your browser's memory, not a server quota.