What is the regex for snake_case word?

The regex pattern for snake_case word is `^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$`. This pattern validates snake_case identifier (lowercase with underscores).

How do I use this regex in JavaScript?

In JavaScript, create the regex with `const regex = /^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$/;` and test with `regex.test(yourValue)`. It returns `true` if the value matches.

How do I use this regex in Python?

In Python, use `import re; re.match(r'^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$', value)`. The raw string prefix (`r`) prevents Python from interpreting backslashes as escape characters.

Is this regex case-sensitive?

By default, yes. To make it case-insensitive, add the `i` flag in JavaScript (`/^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$/i`) or use `re.IGNORECASE` in Python.

Regex for snake_case Word

Regex Pattern

^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$

snake_case identifier (lowercase with underscores)

Quick Answer

The regex pattern for snake_case word is `^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$`. snake_case identifier (lowercase with underscores). This works in JavaScript, Python, Ruby, PHP, Java, and most regex engines that support PCRE syntax.

Test Examples

Input	Result
my_variable	✓ Matches
first_name	✓ Matches
get_data_from_api	✓ Matches
myVariable	✗ No match
My_Variable	✗ No match
single	✗ No match
UPPER_CASE	✗ No match

Code Examples

javascript

const regex = /^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$/;
const isValid = regex.test(value);

python

import re
pattern = r'^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$'
if re.match(pattern, value):
    print("valid")

ruby

pattern = /^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$/
if value =~ pattern
  puts "valid"
end

php

if (preg_match('/^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$/', $value)) {
    echo "valid";
}

java

String pattern = "^[a-z][a-z0-9]*(?:_[a-z0-9]+)+$";
boolean isValid = value.matches(pattern);

Frequently Asked Questions

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