How to use the Regex Tester
- Enter or paste your input in the tool above.
- Choose the available options and select Run tool or Process locally.
- Review, copy, or download the generated result.
What does the Regex Tester do?
The tester uses the browser JavaScript RegExp engine. Pattern and flags are kept separate so you can experiment with global, case-insensitive, multiline, Unicode, or dotAll behaviour.
Common uses
- Develop validation and extraction patterns
- Inspect capture groups and match offsets
- Reproduce browser-side regex behaviour
Regex Tester example
Example input
Contact dev@example.com or team@example.orgExample output
[
{ "match": 1, "value": "dev@example.com", "index": 8 },
{ "match": 2, "value": "team@example.org", "index": 27 }
]Limitations and important notes
- Regex syntax differs between programming languages
- Catastrophic backtracking can make a pattern slow
- A regex is not a complete parser for complex languages
Private browser-based processing
Your data is processed locally in your browser and is not uploaded or stored on our servers. Tool inputs are not saved to local storage.
Regex Tester features
- Free to use with no registration
- Fast client-side processing
- Clear validation and useful error messages
- Copy and download support
- Mobile-friendly accessible interface
Frequently asked questions
Which regular-expression syntax is supported?
The tool uses the JavaScript RegExp syntax supported by your browser.
What does the g flag do?
The global flag finds all non-overlapping matches instead of stopping after the first.
Is the Regex Tester free to use?
Yes. The Regex Tester is completely free and requires no account or installation.
Is my data uploaded when using Regex Tester?
No. Your input and result are processed locally inside your browser and are not sent to our server.
Can I use Regex Tester on mobile?
Yes. The tool works in modern desktop and mobile browsers.