Regex Validator
FAQ
What is this regex validator tool used for?
It allows you to test regular expressions in real time directly in the browser. You can instantly see matching results, capture groups, named groups, and highlighted matches to help you understand and debug regex patterns.
Which regex flags are supported?
The tool supports common JavaScript regex flags:
- g: find all matches
- i: case-insensitive matching
- m: multiline mode (^ and $ apply to each line)
- s: dot matches newline characters
- u: Unicode mode for improved character handling
- y: sticky matching (starts from the current position)
- v: advanced Unicode mode (may not be fully supported in all browsers)
If a flag combination is invalid, the browser will show an error.
Why do some matches look incomplete or missing?
This usually happens for a few reasons:
- The global flag (g) is not enabled, so only the first match is returned
- The regex pattern restricts matches (e.g. using ^ or $ anchors)
- The pattern uses zero-width matching rules that do not consume characters
- Some advanced patterns may affect how matches are found in sequence
What is a zero-width match, and why does it look empty?
A zero-width match is a match that does not consume any characters, such as word boundaries (\b), start of line (^), or end of line ($). These matches appear empty because they represent positions rather than visible text, but the tool highlights them to show where they occur.
What are named capture groups?
Named capture groups allow you to assign a name to a part of your regex using syntax like (?<name>...). Compared to numeric groups, named groups make results easier to understand and access because you can refer to them by name instead of index.
Why does my regex produce an error?
A regex error occurs when the pattern is invalid, such as mismatched parentheses, incorrect escape sequences, or unsupported flag combinations. The tool will display the specific error message to help you identify and fix the issue.
Is my input data sent to a server?
No. All regex processing is done locally in your browser. Nothing you enter is uploaded or stored on a server.
Why do matches sometimes seem duplicated or skipped?
Some regex patterns affect how matches are found in sequence. The tool includes built-in safeguards to prevent incorrect behavior or infinite loops, which may slightly affect how results are displayed but ensures stability.
What is the v flag?
The v flag is an advanced Unicode mode that enables more powerful character set and pattern matching features. Browser support may vary, so behavior can differ depending on the environment.