Regex Tester: Test Regular Expressions Online
Test a JavaScript regular expression online and inspect highlighted matches. Verify the pattern again in your target runtime.
This tool processes its main input in your browser and does not send it to an external API. Fonts and interface assets may load from external providers.
Regex Tester: Test Regular Expressions Online
The regex tester shows which parts of sample text match a regular expression. Patterns and flags follow the JavaScript regular-expression engine used by this page; the interface lists full matches, not capture groups.
Try small examples when building validation, extraction or find-and-replace patterns. A result here does not guarantee identical behavior in another programming language.
How to use it
- Enter a JavaScript regular-expression pattern and any required flags.
- Add sample text and review the highlighted full matches.
- Try edge cases and retest the pattern in the target runtime.
Example
Input: ^\d{4}-\d{2}-\d{2}$ with 2026-10-01
Output: The complete string matches the YYYY-MM-DD shape.
Who is it for?
- Software developers
- Analysts inspecting text logs
- Students learning regular expressions
Privacy and limitations
The pattern and sample are tested in this browser; the regex operation is not sent to an API. Avoid pasting confidential logs.
JavaScript Regular Expressions: Patterns, Flags and Testing
Frequently asked questions
Does regex work the same in every language?
No. Groups, escapes and flags vary between regex engines. Retest patterns in the runtime you will ship.
Why did the pattern find no match?
Check anchors, case-sensitivity flags, line endings and spaces in your sample.
Can a regular expression be slow?
Some nested or greedy patterns can be expensive on certain inputs. Test realistic long strings before production use.
Does this page list capture groups separately?
No. It displays complete matches and highlights them. Use your target runtime to inspect numbered or named capture groups.