---
title: "Regex Tester | Free DevOps Tool | FOSSA"
description: "Free online regex tester and debugger with syntax highlighting, real-time matching, and detailed match information. Test and validate regular expressions instantly."
canonical_url: "https://fossa.com/resources/devops-tools/regex-tester/"
markdown_url: "https://fossa.com/resources/devops-tools/regex-tester.md"
language: "en"
author: "FOSSA"
organization: "FOSSA"
---

# Regex Tester | Free DevOps Tool | FOSSA

> Free online regex tester and debugger with syntax highlighting, real-time matching, and detailed match information. Test and validate regular expressions instantly.

## Regex Tester

Build and test regular expressions with real-time feedback and highlighting.

/

/gm

Use $1, $2, etc. to reference captured groups. Use $& to reference the entire match.

Enter a regular expression to see matches

### Regular Expression Reference

Regular expressions (regex) are patterns used to match character combinations in strings. They are powerful tools for text processing, validation, and search operations.

#### Basic Syntax

##### Character Classes

- `.` \- Any character except newline
- `\w` \- Word character \[a-zA-Z0-9\_\]
- `\d` \- Digit \[0-9\]
- `\s` \- Whitespace character
- `[abc]` \- Any of a, b, or c
- `[^abc]` \- Not a, b, or c
- `[a-z]` \- Any character a through z

##### Quantifiers

- `*` \- 0 or more, equivalent to {0,}
- `+` \- 1 or more, equivalent to {1,}
- `?` \- 0 or 1, equivalent to {0,1}
- `{3}` \- Exactly 3 times
- `{3,}` \- 3 or more times
- `{3,5}` \- Between 3 and 5 times

##### Anchors

- `^` \- Start of string/line
- `$` \- End of string/line
- `\b` \- Word boundary
- `\B` \- Not word boundary

##### Groups & Alternation

- `(abc)` \- Capture group
- `(?:abc)` \- Non-capturing group
- `a|b` \- Match a or b
- `(?<name>abc)` \- Named capture group

#### Common RegEx Patterns

Email Address

`^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$`

URL

`https?:\/\/[\w\d\-\.]+\.\w{2,}[\w\d\-\.\/\?\=\&\%]*`

IPv4 Address

`\b(?:\d{1,3}\.){3}\d{1,3}\b`

ISO Date

`\d{4}-\d{2}-\d{2}`

##### Regex Best Practices

- Start simple and build complexity incrementally
- Use non-capturing groups (?:) when you don't need the captured value
- Be careful with greedy quantifiers (\* and +) which can lead to unexpected results
- Test with various inputs, including edge cases
- Consider performance implications for large inputs

### Get Started with FOSSA

Start managing your dependencies, licenses, and vulnerabilities today.

## Source

Canonical page: https://fossa.com/resources/devops-tools/regex-tester/