What is Regex Tester?
Regex Tester is a playground for writing and debugging regular expressions. It highlights matches in real time as you type your pattern, displays capture groups, and lets you test replacement patterns with backreferences. Whether you are writing a validation rule, parsing log entries, or building a text transformation, this tool provides immediate visual feedback.
Regular expressions are powerful but notoriously tricky. A misplaced quantifier, a missing escape character, or an incorrect group boundary can produce unexpected matches or catastrophic backtracking. DevKit’s Regex Tester shows you exactly what your pattern matches, making it easy to iterate toward the correct expression.
How to Use Regex Tester
Type your regex pattern in the pattern field. Paste your test text in the input area below. Matches highlight immediately. Toggle flags (global, case-insensitive, multiline, dotAll) using the flag buttons to change matching behavior.
The match panel lists every match with its position, full match text, and named or numbered capture groups. For replacement testing, enter a replacement template using $1, $2, or $<name> backreferences and preview the transformed text.
The built-in pattern library provides starting points for common tasks: email validation, URL extraction, date parsing, IP address matching, and more.
Common Use Cases
- Input validation: Build and test regex patterns for form validation: email addresses, phone numbers, postal codes, and custom input formats.
- Log parsing: Write expressions to extract timestamps, error codes, request IDs, and other structured data from unstructured log lines.
- Data extraction: Develop patterns for scraping or transforming text data, extracting specific fields from CSV, TSV, or fixed-width formats.
- Search and replace: Prototype complex find-and-replace operations with capture groups before running them on production data or code.
- Code generation: Test regex patterns before embedding them in application code, ensuring they handle edge cases correctly.