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camelCase to snake_case

camelCase is common for JavaScript / TypeScript / Java variables and JSON keys in many web APIs; snake_case is used for Python variables, Ruby, database columns and many REST APIs. Moving data between languages, databases and APIs often means converting between the two.

Examples

camelCase snake_case
userId user_id
firstName first_name
createdAt created_at
XMLHttpRequest xml_http_request
orderItemId order_item_id

Try it

camelCase 
 
 
 PascalCase  
 
 
 
 snake_case  
 
 
 
 CONSTANT_CASE  
 
 
 
 kebab-case  
 
 
 
 Train-Case  
 
 
 
 dot.case  
 
 
 
 path/case  
 
 
 
 Title Case  
 
 
 
 Sentence case  
 
 
 
 lowercase  
 
 
 
 UPPERCASE  
 
 
 
 
  
 
    
In code
 
 
 
JavaScript
 
const toSnake = (s) => s
  .replace(/([a-z\d])([A-Z])/g, '$1_$2')
  .replace(/([A-Z]+)([A-Z][a-z])/g, '$1_$2')
  .toLowerCase();
 
 
Python
 
import re

def to_snake(s: str) -> str:
    s = re.sub(r'([A-Z]+)([A-Z][a-z])', r'\1_\2', s)
    return re.sub(r'([a-z\d])([A-Z])', r'\1_\2', s).lower()
 
 
  
More examples
  
 Open the full Case Converter →