Regex Tester Online – Test JavaScript Patterns

Local only

Check whether a JavaScript regular expression matches your sample text and catch invalid pattern syntax locally.

27 chars · 1 line

5 chars · 1 line

Pattern matched the inputFlags: g

Regex testing guide

How to test a regular expression against sample text

Enter a JavaScript regex pattern and flags above, paste the text you want to check, and keep Test selected for a direct Match or No match result. Invalid patterns and flags are reported before the sample text is evaluated. This tool is free to use. No account or payment is required.

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What you can do here

  • JavaScript RegExp compilation
  • Match or No match output
  • Configurable regex flags
  • Syntax error feedback
  • Local text testing
  • Browser-local processing

Steps

  1. Enter the pattern without surrounding slash delimiters.
  2. Add JavaScript flags such as i, m, s, u, or g when the pattern needs them.
  3. Paste the sample text into the input panel and keep Test selected.
  4. Correct any syntax error, then use the Match or No match result in your debugging workflow.

Validate JavaScript RegExp syntax before testing text

VetaTool compiles the pattern using the browser's RegExp constructor. Missing parentheses, malformed character classes, unsupported flags, and duplicate flags therefore fail before a text result is shown.

This page tests JavaScript regex behavior specifically, so a pattern copied from PCRE, Python, .NET, or another flavor may require changes before it compiles.

Use flags to control the matching rules

Case-insensitive, multiline, dotAll, Unicode, sticky, and other supported JavaScript flags change how the same pattern is evaluated. Test mode preserves the flags exactly as entered and does not automatically add a global scan.

Test logs and source snippets without uploading them

The pattern and sample text are evaluated in the browser. That is useful when the test input contains private logs, identifiers, stack traces, or copied application text that should not be sent to a remote regex service.

Regex tester example

A case-insensitive word-boundary pattern matches the product name even though the sample text uses different capitalization.

Pattern and sample

/\bvetatool\b/i
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Test result

Match

Common questions

Frequently asked questions

Should I include /slashes/ around the regex pattern?

No. Enter only the pattern body in the Pattern field and put flags such as g or i in the Flags field.

Does Test mode find every match?

No. Test mode answers whether at least one match exists. Use Regex Matcher when you need every occurrence and capture group.

Why does a regex from another language fail?

Regex flavors differ. This tool follows JavaScript RegExp syntax and browser support rather than PCRE, Python, Java, or .NET rules.

Recommended next steps

Regex Matcher Online – Find All MatchesEnumerate every match and inspect numbered or named captures.Regex Replacer Online – Find & Replace TextPreview JavaScript replacement tokens against matching text.Regex Tester, Matcher & ReplacerSwitch between all regular-expression operations in one workspace.

Debugging a specific Regex issue? Browse Regex troubleshooting.