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description=Free online regex tester. Test JavaScript regular expressions with live match highlighting, capture group extraction, and full flag support (g, i, m, s).;
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Text of the page (random words):
regex tester test regular expressions online skip to main content sadiqbd free online tools calculators all calculators emi loan calculator emi loan planner simple interest calculator compound interest calculator sip calculator fixed deposit fd calculator recurring deposit rd calculator recurring deposit rd goal planner retirement calculator inflation calculator percentage calculator date calculator gst vat calculator converters all converters length converter weight converter temperature converter area converter volume converter speed converter time converter data storage converter pressure converter energy converter power converter angle converter frequency converter fuel economy converter cooking converter time zone converter currency exchange text tools all text tools word character counter case converter text reverser lorem ipsum generator remove duplicate lines sort lines text diff find replace text to slug string repeater morse code translator rot13 encoder character frequency 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all text tools word character counter case converter text reverser lorem ipsum generator remove duplicate lines sort lines text diff find replace text to slug string repeater morse code translator rot13 encoder character frequency text truncator whitespace cleaner health all health age calculator bmi calculator bmr calculator ideal body weight calories burned calculator steps to calories calorie intake calculator daily water intake calculator sleep calculator macro calculator body fat calculator height converter period calculator pregnancy due date calculator internet all internet subnet calculator ping traceroute dns lookup mx lookup ns lookup spf lookup generator dkim checker dmarc lookup generator bimi lookup generator email blacklist checker whois lookup port scanner http headers checker ssl checker reverse dns lookup website speed test developer all developer json formatter json unescape cleaner json diff base64 encoder decoder url encoder decoder html entities password generator uuid generator timestamp converter number base converter jwt decoder regex tester color converter hash generator bcrypt generator random string generator cron explainer rest api checker seo all seo serp preview meta tag generator open graph generator keyword density robots txt generator xml sitemap generator utm builder schema generator hreflang generator canonical tag generator link extractor image alt checker redirect mapper heading extractor seo checklist blog all blog calculators converters text tools health internet developer seo home developer regex tester test regular expressions online regex tester test javascript regular expressions with live match highlighting capture group extraction and full flag support g i m s type your regex pattern without slashes toggle the g i m s flags as needed paste the text you want to match against matches are highlighted and listed in real time pattern g i m s test string highlighted matches match list common patterns email url ipv4 phone date yyyy mm dd hex color acronyms numbers frequently asked questions what regex flags do g i m and s do g global find all matches not just the first i case insensitive treat uppercase and lowercase as equivalent m multiline make and match the start and end of each line not just the whole string s dotall make match newline characters n r in addition to all other characters without s does not match newlines what is the difference between and s w d matches any single character except newline unless s flag d matches any digit 0 9 w matches a word character a za z0 9_ s matches any whitespace character space tab newline carriage return their uppercase counterparts d w s match the inverse any non digit non word or non whitespace character respectively what are capture groups and how do i use them a capture group is a portion of a regex enclosed in parentheses that captures the matched substring for later use groups are numbered from 1 left to right example d 4 d 2 d 2 on 2024 01 15 captures 2024 in group 1 01 in group 2 15 in group 3 named groups use name pattern syntax non capturing groups use pattern to group without capturing what is the difference between greedy and lazy quantifiers greedy quantifiers n m match as much as possible on a and b matches the entire a and b lazy reluctant quantifiers n m match as little as possible on the same input matches only a use lazy quantifiers when you need to match the shortest possible string between delimiters how do lookahead and lookbehind work lookahead asserts what comes after the current position without consuming characters example w s is matches the word before is negative lookahead asserts that a pattern does not follow lookbehind asserts what comes before negative lookbehind asserts what does not come before lookbehind is supported in modern javascript es2018 but not in older environments what does b word boundary match b is a zero width assertion that matches the position between a word character w and a non word character it does not consume any characters bword b matches the whole word word but not password or wording use it to match complete words bcat b matches cat in the cat sat but not in concatenate how do i match special regex characters literally escape the special character with a backslash the special characters that need escaping in regex are example to match a literal period use instead of to match a literal dollar sign use when building regex from user input in code use a function to escape all special characters str replace g what causes catastrophic backtracking catastrophic backtracking redos occurs when a regex with nested quantifiers takes exponential time to fail example a b against a long string of a s with no b the engine tries an exponential number of grouping combinations before giving up mitigation avoid nested quantifiers with overlapping possibilities use atomic groups or possessive quantifiers where available and validate user supplied regex patterns before applying them to untrusted input use this tester to measure performance before production use how is javascript regex different from pcre or python regex javascript regex ecmascript lacks some features found in pcre and python no recursive patterns no conditional patterns no branch reset groups no possessive quantifiers though atomic groups were added in es2022 via javascript added named capture groups name lookbehind and s dotall flag in es2018 javascript s u flag enables full unicode mode this tester uses javascript regex patterns from other flavors may behave differently how do i match multiple lines in javascript regex use the m multiline flag to make and match the start and end of each line use the g global flag with string matchall to find all occurrences across lines to match content spanning multiple lines use the s dotall flag to make match newlines or use s s as a universally compatible alternative example start s s end m matches from start to end across lines about this regex tester this free regex tester tests javascript regular expressions with real time match highlighting and capture group extraction all matching runs in your browser using the native javascript regex engine no data is sent to any server when to use this tool building and testing patterns for input validation debugging regex patterns that don t match as expected exploring capture groups and backreferences testing regex flags global case insensitive multiline dotall related developer tools json formatter html entities url encoder cron explainer return idx 1 esc m 0 at index m index groups join document getelementbyid rxmatchlist innerhtml listhtml mcard style display function esc s return s replace g replace replace g related articles in depth guides and technical articles view all developer jun 24 2026 missing a regex anchor is a bug why and b work differently than you think in multiline mode the difference between a regex that matches digits and one that matches only digits is anchor characters and missing anchors are why input validators accept strings they should reject here s how and change behavior in multiline mode a security relevant surprise why b word boundaries break on unicode text the z vs distinction for absolute string end matching in python and why unanchored authorization patterns misclassify urls developer jun 16 2026 regex readability how verbose mode and named capture groups turn a mystery into documentation two regexes can match identical strings while one takes 30 seconds to understand and the other takes 10 minutes and the difference is almost always structural not functional here s how verbose extended mode adds comments and whitespace to patterns why named capture groups document intent within the pattern itself a mental library of common recognizable patterns and when a single complex regex should be replaced with simpler sequential operations instead developer jun 14 2026 named capture groups lookahead and lookbehind modern regex features that make patterns readable named capture groups turn regex matches from numbered tuples into readable dictionaries lookahead and lookbehind assertions match positions without consuming characters here s the modern regex feature set named groups non capturing groups all four assertion types with practical patterns for log parsing and url extraction developer jun 9 2026 redos how catastrophic backtracking in a single regex can take down a server a single regex with a crafted input knocked stack overflow offline for 34 minutes and caused a global cloudflare outage here s how catastrophic backtracking works which patterns are vulnerable how to test for redos and how to write safe alternatives developer jun 8 2026 regex patterns every developer should have a practical reference a practical reference of the regex patterns developers actually need email url uuid ip address dates semver hex colours slugs and more with edge cases and caveats for each sadiqbd 100 free online tools for finance health development and seo no sign up required tools calculators converters text tools health internet developer seo company about blog glossary privacy policy terms 2026 sadiqbd platform all rights reserved rate us on trustpilot install sadiqbd add to your home screen for quick access install install on iphone ipad tap share then add to home screen