Regex Tester
Test and validate regular expressions by entering a pattern, flags, and sample text.
The tester highlights matches, displays the number of hits, and shows captured groups
to help you understand how your regular expression behaves.
You can freely combine flags such as global, case-insensitive, or multiline, and instantly see the results reflected in the output.
Syntax errors are detected immediately and shown as clear error messages, making it easier to debug and refine complex patterns.
This tool is useful for developers, data analysts, and anyone working with text processing, log analysis, form validation, or search patterns.
All testing is performed locally in your browser, and no input text or patterns
are sent to any server, allowing safe and private experimentation.
How to use & features
- Enter the pattern and flags at the top, then paste the target text into the input area below.
- Matched portions are highlighted, and capture group values are shown for inspection.
- Type a replacement string to see the output update in real time.
- All processing runs locally, so your text is never sent anywhere.
Sample input & output
Find email addresses
Input
Pattern: /[\w.-]+@[\w.-]+/g Text: Contact us at support@example.com today.
Output
Matches: ["support@example.com"]
Frequently asked questions
Which regex engine is used?
Can I set flags?
How long can the test text be?
Common use cases
Iterating on search patterns
Test regexes against sample text to tune matches for replace or extraction logic.
Creating shareable examples
Keep patterns alongside test strings so reviews and questions convey intent clearly.
Sanity-checking performance
Vary input sizes to spot catastrophic backtracking issues before shipping.
Notes & limitations
Work stays in your browser
Inputs and outputs remain local. Closing the tab or clearing cache will remove any temporary state.
Validate critical data
Results are helper outputs—double-check them before sending to production systems or sharing externally.
Large payloads depend on your device
Very large text or files can feel slow in some browsers. Use a desktop environment for heavy workloads.