Regex Validator
Test and validate regular expressions with live matching. See all matches, capture groups, and common patterns instantly.
Regular Expression Pattern
Test String
📚 Common Patterns:
How to Validate Regular Expressions
Step 1: Enter Regex Pattern
Type your regular expression pattern. Example: \\d3-\\d3-\\d4 for phone numbers. Click "Sample" to see an email regex.
Step 2: Enter Test String
Paste text to test against the regex pattern. The tool will find all matches instantly.
Step 3: Set Flags
Choose regex flags: g = global (find all), i = case-insensitive, m = multiline, s = dotall.
Step 4: View Results
See all matches with their positions and capture groups. Use common patterns as quick templates.
Step 5: Copy Results
Copy the validation results to use in your application or documentation.
Frequently Asked Questions
What is a regular expression?
A regex is a pattern used to match text. It's used for validation, search, replace, and text processing in all programming languages.
What do the flags mean?
g = Find all occurrences (global), i = Ignore case, m = Treat as multiline, s = Dot matches newline.
What are capture groups?
Groups are parts of the pattern in parentheses. They "capture" matching text for reuse. Access with $1, $2, etc.
How do I match digits?
Use \\d for a single digit, \\d3 for exactly 3 digits, \\d+ for one or more, \\d* for zero or more.
What's the difference between . and \d?
. matches any character (except newline), \\d matches only digits 0-9.
What about anchors like ^ and $?
^ matches the start of a string, $ matches the end. ^hello$ matches only "hello" exactly.
How do I escape special characters?
Use backslash \\ before special chars. For example, \\. matches a literal dot, \\$ matches a dollar sign.
Can I use character classes?
Yes, [a-z] matches lowercase, [A-Z] matches uppercase, [0-9] matches digits, [^a-z] matches anything except lowercase.
What about alternation?
Use the pipe | for OR. cat|dog matches either "cat" or "dog". Use parentheses for grouping: (cat|dog)s matches "cats" or "dogs".
Is my data private?
Yes, all regex testing happens in your browser. Your patterns and test strings are never sent to any server.
About Regular Expressions
Regular expressions are essential for modern development:
- Form Validation: Validate email, phone, URL, and other formats
- Text Search: Find and extract specific patterns from text
- Data Cleaning: Remove or replace unwanted text patterns
- String Parsing: Extract structured data from unstructured text
- Format Conversion: Transform data from one format to another
- Code Generation: Find and modify code patterns automatically
- Log Analysis: Extract relevant information from log files
- Cross-Language: Regex works in Python, JavaScript, Java, C#, PHP, Ruby, and more