Representative example
This example reflects the implemented transformation or analysis.
Input
Pattern: (\w+)@(\w+\.\w+) /g
Text: mail dev@motifuse.devOutput
1 match: dev@motifuse.dev
$1="dev" $2="motifuse.dev"Regex Tester
Test JavaScript regular expressions against sample text with live match highlighting, capture groups, match counts, and flag controls.
- Free public tool
- No sign-up for this tool
- Processing clearly labeled
- Instant results
Content last reviewed
60 characters · 1 lines
2 matches
Contact us at hello@motifuse.dev or sales@example.com today.
Quick Start
Add input
Enter a JavaScript regex pattern, flags, and representative test text.
Choose options
Flags g, i, m, s quick toggles; the field also accepts valid gimsuy flags.
Review the result
Check the output or diagnostics, then use the available copy or download control where shown.
Examples
Input and output example 1
Input
Pattern: (\w+)@(\w+\.\w+) /g
Text: mail dev@motifuse.devOutput
1 match: dev@motifuse.dev
$1="dev" $2="motifuse.dev"About the Regex Tester
Regex Tester addresses a focused developer workflow without requiring a command-line setup. Test JavaScript regular expressions against sample text with live match highlighting, capture groups, match counts, and flag controls. Results update from the supplied input, making it useful for quick inspection, debugging, documentation, or test preparation.
In this tool, Regex Tester: processing runs in the browser and the tool does not call an external conversion API. Input remains in page memory unless a confirmed browser feature such as file reading or local settings is described above.
How to Use Regex Tester
Enter a JavaScript regex pattern, flags, and representative test text.
Configure flags g, i, m, s quick toggles; the field also accepts valid gimsuy flags.
Review the generated output, status, or validation message.
Copy or download the result when that control is available, and verify it in the destination where it will be used.
Key Features
Focused processing
The browser constructs
new RegExp(pattern, flags). Global mode iterates every match, protects against zero-length loops, and records captures and indexes.Input guidance
JavaScript regular-expression syntax and plain text.
Immediate feedback
Invalid patterns or duplicate/incompatible flags show the native regular-expression error.
When to Use Regex Tester
Application development
Use Regex Tester to prepare or inspect values while implementing a feature.
Fault isolation
Run a small known input through Regex Tester to distinguish formatting or syntax problems from surrounding application behavior.
Reviewable examples
Create a concise 1 match: dev@motifuse.dev for tests, documentation, or code review.
How It Works
Processing flow
The browser constructs new RegExp(pattern, flags). Global mode iterates every match, protects against zero-length loops, and records captures and indexes.
Result handling
During processing, Regex Tester: the result is rendered directly in the tool interface. Validation failures are displayed instead of being silently treated as successful output.
Supported Formats and Options
Formats
Accepted input
JavaScript regular-expression syntax and plain text
Displayed output
1 match: dev@motifuse.dev
Options
Available controls
Flags g, i, m, s quick toggles; the field also accepts valid gimsuy flags
Common Errors and Troubleshooting
Common errors
Invalid or incomplete input
Invalid patterns or duplicate/incompatible flags show the native regular-expression error.
Unexpected result
Confirm that the selected mode or syntax matches the source and that the input is complete.
Troubleshooting guide
Resolve the reported error
Invalid patterns or duplicate/incompatible flags show the native regular-expression error. Reduce the input to the smallest failing case and confirm the selected controls.
Check an unexpected result
Review the documented limitation for Regex Tester, then compare a known example with the same mode or syntax before processing a larger value.
Limitations and Important Notes
Behavior follows the current JavaScript regex engine, which differs from PCRE, Python, .NET, and other flavors.
Privacy and Data Processing
Regex Tester performs its implemented transformation in the browser without calling an external processing API. Input is held in the current page state, so still avoid unnecessary secrets and clear the field on a shared device.
Tips and Best Practices
Practical tips
Keep the original javascript regular-expression syntax and plain text before using Regex Tester.
Exercise the error case described as: Invalid patterns or duplicate/incompatible flags show the native regular-expression error.
Check the result against this limitation: Behavior follows the current JavaScript regex engine, which differs from PCRE, Python, .NET, and other flavors.
Best practices
Prepare a representative input
Start with a small value whose expected result you understand, then add the edge cases relevant to Regex Tester. Preserve the original when the conversion or formatting is destructive.
Verify in context
Behavior follows the current JavaScript regex engine, which differs from PCRE, Python, .NET, and other flavors. Treat the displayed result as an intermediate artifact and test it in the runtime, parser, database, or document where it will actually be used.
Technical Details
Implementation note: Regex Tester: the browser constructs new RegExp(pattern, flags). Global mode iterates every match, protects against zero-length loops, and records captures and indexes.
Who Is This For?
Developers, QA engineers, technical writers, analysts, and students who need test JavaScript regular expressions against sample text with live match highlighting, capture groups, match counts, and flag controls.
Frequently Asked Questions
Does Regex Tester send input to an API?
No external processing API is used by this tool; its implemented operation runs in the browser.
What input is supported?
JavaScript regular-expression syntax and plain text.
Why did the tool show an error?
Invalid patterns or duplicate/incompatible flags show the native regular-expression error.
What should I verify before using the result?
Behavior follows the current JavaScript regex engine, which differs from PCRE, Python, .NET, and other flavors.