Regex Tester
Test regular expressions with live matching results.
How to use the Regex Tester
A regular expression (regex) is a pattern used to match sequences of characters in text. This tool lets you write a pattern, pick flags, and test it against any string — all without leaving your browser.
- 1
Enter your regex pattern
Type a pattern in the Pattern field, for example
\d+to match one or more digits, or^[a-z]+$to match lowercase-only strings. - 2
Select flags
Check Global to find all matches (not just the first), Case Insensitive to ignore letter case, or Multiline to let
^and$match line starts and ends. - 3
Paste your test text
Type or paste the text you want to search into the large textarea. The tool scans the entire string for matches against your pattern.
- 4
Read the match results
Matches appear instantly below, showing the matched text and the character index where each match was found in the string.
Frequently asked questions
What is a regular expression?
A regular expression is a sequence of characters that defines a search pattern. Regex is supported in every major programming language and is used to search, validate, and transform text efficiently — from simple word searches to complex parsing tasks.
What do ^ and $ anchors do?
^ matches the start of the string (or start of each line when the Multiline flag is on). $ matches the end. Together they let you assert that the entire input matches your pattern, not just a substring within it. For example, ^\d+$ matches strings that are entirely numeric.
What are capturing groups?
Parentheses (...) create a capturing group that saves the matched text for later use. For example, (\d4)-(\d2)-(\d2) captures year, month, and day separately from a date string. Non-capturing groups use (?:...).
What are some common regex patterns?
Email (simple): ^[^\s@]+@[^\s@]+\.[^\s@]+$ · digits only: ^\d+$ · URL: https?:\/\/[\w./-]+ · whitespace runs: \s+ · word boundary: \b\w+\b · hexadecimal color: #[0-9a-fA-F]6.
What do the flags g, i, and m mean?
g (Global) finds every match rather than stopping at the first. i (Case Insensitive) treats uppercase and lowercase letters as equal. m (Multiline) makes ^ and $ match the start and end of each line instead of the whole string.
How do I escape special characters?
Precede special characters with a backslash. For example, \. matches a literal dot, \( matches an open parenthesis, and \$ matches a dollar sign. Without the backslash, characters like . * + ? ^ $ [ ] | ( ) have special meanings in regex syntax.
Can regex cause browser slowdowns?
Yes — poorly written patterns on large inputs can trigger catastrophic backtracking. Avoid nested quantifiers like (a+)+ and test with realistic data before using patterns in production code or against untrusted user input.