Go RegEx Tester

What is Go Regex?

In Go (or Golang), regular expressions are supported through the regexp standard package. They allow you to search, match, replace, and extract text patterns using concise and powerful syntax.

Go regex patterns are often used for:

• Validating inputs (emails, phone numbers, etc.)

• Extracting tokens from strings or logs

• Processing or cleaning up text

• Implementing conditional logic in parsing systems

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Unlike JavaScript or Python, Go’s regex engine does not support lookbehinds—but it’s optimized for performance, making it perfect for high-throughput applications.

Go Regex Tester by Qodex

The Go Regex Tester helps you test, validate, and debug your regular expressions in real time using Go syntax. Instantly see matches, capture groups, errors, and behavior of different regex patterns—no setup or compilation needed.

Want to generate test inputs? Try these:

• Email Generator

• Phone Number Generator

• Password Generator

• UUID Generator

  
  

Core Constructs of Go Regex Tester

• Real-Time Matching – Instantly see matches, capture groups, and test outputs as you type.

• Supports Golang Syntax – Built to mimic regexp package behavior accurately.

• Sample Test Strings – Easily plug in realistic data for validation.

• Error Debugging – Get immediate feedback on invalid syntax.

• Integrated Tools – Combine with UUID Generator, MAC Address Generator, or Token Generator for complete test environments.

How It Works (Quick Guide)

1. Enter your regular expression in the input field.

2. Add a test string to match against.

3. See matched text and captured groups instantly.

4. Use dummy data from Email Generator, Phone Number Generator, or Credit Card Generator to simulate real-world input.

Example Use Cases

• Validating email addresses in Go web forms

• Extracting error codes from system logs

• Checking password strength in APIs

• Parsing phone numbers from user input

• Detecting keywords or mentions in text

Go Regex Meta Characters

Basic Matching

• . : Matches any character except newline characters (\n).
  Example: /a.b/ matches "acb", "a9b", but not "ab".

  
  

• ^ : Matches the start of a string.

  Example: /^Log/ matches "Log message" but not "My Log".

  
  

• $ : Matches the end of a string.

  Example: /end$/ matches "game end" but not "ending game".

  
  

• | : Acts as an OR between two patterns.

  Example: /cat|dog/ matches "cat" or "dog".

Character Classes

• [abc] : Matches 'a', 'b', or 'c'.

• [^abc] : Matches any character except 'a', 'b', or 'c'.

• [a-zA-Z] : Matches any letter from a to z or A to Z.

  
  

Predefined Character Classes

• \d : Matches any digit (0–9).

• \D : Matches any non-digit.

• \s : Matches whitespace (space, tab, newline).

• \S : Matches any non-whitespace character.

• \w : Matches letters, digits, or underscores.

• \W : Matches any non-word character.

  
  

Quantifiers

• * : Matches zero or more of the preceding element.

• + : Matches one or more.

• ? : Matches zero or one (optional).

• {n} : Matches exactly n times.

• {n,} : Matches at least n times.

• {n,m} : Matches between n and m times.

  
  

Groups and Assertions

• (...) : Capturing group.

• (?:...) : Non-capturing group.

• (?=...) : Positive lookahead.

• (?!...) : Negative lookahead.

• \b : Word boundary.

• \B : Non-word boundary.

  
  

Note: Golang does not support lookbehind assertions like (?<=...) or (?<!...).

Tips for Using Go Regex Tester

• Use regexp.MustCompile() for performance-safe compiled regex.

• Preload test strings using the Phone Number Generator or Zipcode Generator.

• Validate patterns in real time before embedding in your Golang application.

• Keep complex patterns readable with comments or separate lines.

  
  

Go Regex Tester Examples

Example 1: Validate Email

Use the Email Generator to generate realistic test emails.

package main
import (
    "fmt"
    "regexp"
)

func main() {
    email := "test@qodex.ai"
    re := regexp.MustCompile(`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`)
    fmt.Println(re.MatchString(email))
}

Example 2: Check Password Strength

Use the Password Generator to generate secure passwords.

package main

import (
  "fmt"
  "regexp"
)

func main() {
  password := "Aa123456!"
  pattern := regexp.MustCompile(`(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&]).{8,}`)
  fmt.Println("Strong Password:", pattern.MatchString(password))
}

Example 3: Extracting All Words from Text

Combine with the Username Generator to simulate identity parsing.

package main

import (
  "fmt"
  "regexp"
)

func main() {
  text := "Go is simple, fast, and powerful!"
  pattern := regexp.MustCompile(`\b\w+\b`)
  words := pattern.FindAllString(text, -1)
  fmt.Println("Words Found:", words)
}

Pro Tips for Golang Regex Tester

• Use regexp.MustCompile() for safe and efficient regex creation.

• Test using realistic data—pair with tools like Phone Generator or UUID Generator.

• Go regex does not support lookbehinds, so adjust patterns accordingly.

• Always escape backslashes (\\) when writing Go strings.

• For better readability and debugging, break complex regex into smaller parts.

Best Tools to Combine With:

• Email Generator

• Password Generator

• UUID Generator

• Credit Card Generator

• Phone Number Generator