Regex Matcher Online – Find All Matches
Find all JavaScript regex matches online, inspect indexes and capture groups, and test patterns locally without uploading your text.
Regular Expressions topic hub
Regex tools, examples and common pattern fixes
Test and debug JavaScript regular expressions, inspect matching and capture groups, practice replacements, and find practical fixes for common pattern errors.
Start by testing a pattern against sample text, then check flags, anchors and capture groups. Use the troubleshooting examples when a match fails or a replacement behaves unexpectedly, and the guide for syntax reference.
Recommended starting points
Featured
4 resources
JavaScript Regex Cheat Sheet – Quick Reference & Examples
JavaScript regex quick reference for character classes, anchors, quantifiers, groups, lookarounds, flags, replacements, and copyable examples.
Regex Tester Online – Test JavaScript Patterns
Test JavaScript regular expressions locally, validate pattern and flags, and see whether sample text matches without uploading logs or snippets.
Regex Troubleshooting & Error Fixes
Troubleshoot JavaScript regular-expression syntax, flags, anchors, quantifiers, groups, lookarounds, matching behavior, and replacements.
Start here
Core tools
2 resources
Regex Tester Online – Test, Match & Replace
Test JavaScript regular expressions, inspect all matches and capture groups, or replace text locally in your browser with configurable regex flags.
Regex Replacer Online – Find & Replace Text
Replace text with JavaScript regular expressions locally, preview capture-group replacement tokens, and control single or global replacement with regex flags.
Troubleshoot
Problems and fixes
24 resources
Regex * Matches Empty String – Use + When One Is Required
Understand why a JavaScript regex with * can match zero characters and use + when at least one occurrence must be present.
Regex Alternation Precedence – Group OR Patterns with Anchors
Fix JavaScript regex alternation precedence by grouping alternatives before applying ^ and $ anchors or shared surrounding context.
Regex Backslash at End of Pattern – Fix Incomplete Escape
Fix a JavaScript regex that ends with a lone backslash by completing or removing the unfinished escape sequence.
Regex Capture Groups – Inspect Numbered Captures Online
Test JavaScript regex capture groups locally and inspect every numbered capture, match value, and zero-based match index in structured output.
Regex Case Insensitive Match – Use the JavaScript i Flag
Make a JavaScript regex case insensitive with the i flag when uppercase or lowercase text should match the same pattern.
Regex Dot Does Not Match Newline – Use the JavaScript s Flag
Use JavaScript regex dotAll mode when . must match across line terminators, and compare the same pattern with and without the s flag locally.
View all 24
Regex Duplicate Flag Error – Remove Repeated g, i, m Flags
Fix duplicate JavaScript regex flags such as gg or ii by keeping each flag at most once before compiling the pattern.
Regex Escape Dot – Match a Literal Period Instead of Any Character
Escape a dot in JavaScript regex syntax when you need a literal period, not the . wildcard, and test the corrected pattern locally.
Regex Greedy vs Lazy Quantifiers – Compare .* and .*?
Compare greedy and lazy JavaScript regex quantifiers locally when .* consumes more text than intended, using Match All to inspect the difference.
Regex Invalid Flag Error – Fix Unsupported JavaScript Flags
Fix an unsupported JavaScript regex flag by using only browser-supported RegExp flags such as g, i, m, s, u, v, y, or d.
Regex Invalid Quantifier Range – Fix {min,max} Order
Fix a JavaScript regex quantifier such as {3,2} when its minimum repeat count exceeds its maximum count.
Regex Match Whole String – Add Start and End Anchors
Make a JavaScript regex match the entire string instead of a substring by adding ^ and $ anchors, then test the exact-match behavior locally.
Regex Multiline Anchors – Use the JavaScript m Flag
Use the JavaScript regex m flag when ^ and $ should match the start and end of individual lines in multiline text.
Regex Named Capture Groups – Use (?<name>...) in JavaScript
Test JavaScript named capture groups locally and inspect both numbered captures and the named groups object returned for each regex match.
Regex Negative Lookahead – Exclude a Following Pattern
Test JavaScript negative lookahead (?!...) locally to match a token only when an unwanted pattern does not immediately follow it.
Regex Non-Capturing Group – Use (?:...) Without Extra Captures
Use a JavaScript regex non-capturing group (?:...) to group alternatives or quantifiers without adding an unnecessary numbered capture.
Regex Nothing to Repeat Error – Fix Leading Quantifiers
Fix JavaScript regex Nothing to repeat errors caused by *, +, ?, or repetition syntax without a preceding token.
Regex Positive Lookahead – Match Before Following Text
Test JavaScript positive lookahead (?=...) locally to require following text without including that following text in the regex match.
Regex Range Out of Order – Fix Invalid Character Range
Fix a JavaScript regex character range such as [z-a] when the range endpoints are reversed, then retest the corrected class locally.
Regex Replace All – Use the JavaScript g Flag
Compare first-match and replace-all JavaScript regex behavior locally by adding the global g flag to the same pattern and replacement.
Regex Replace Capture Groups – Use $1 and $2 in JavaScript
Preview JavaScript regex replacement with capture-group tokens such as $1 and $2 locally, using the exact String.replace behavior of the browser.
Regex Unclosed Character Class – Fix Unterminated [ ]
Fix an unterminated JavaScript regex character class by closing an opening bracket and retest the corrected pattern locally.
Regex Unclosed Group Error – Fix Unterminated Parentheses
Fix an unclosed JavaScript regex group by finding an opening parenthesis without a matching close, then test the corrected pattern locally.
Regex Word Boundary – Stop Matching Inside Longer Words
Use JavaScript regex word boundaries when a token should match as a word but not as part of a longer identifier or sentence word.