How to convert camelCase to snake_case

JavaScript uses camelCase for variables and functions; Python and SQL use snake_case. When writing a backend that bridges both ecosystems — serialising a JavaScript object to a Python API, or mapping JSON keys to database column names — you need to convert dozens of identifiers at once. This guide shows how to convert any camelCase identifier to snake_case in one step, and how to automate the conversion in a script.

Step-by-step guide

1. Paste the camelCase identifier: Enter the camelCase name — for example 'firstName', 'createdAt', or 'isEmailVerified'. The tool recognises camelCase word boundaries automatically.
2. Select snake_case as the target: Choose 'snake_case' from the target case selector. The output will be all-lowercase with underscores between words.
3. Use in Python or SQL: Copy the result and use it as a Python variable name, a database column name, or a key in a snake_case API payload. In Django or SQLAlchemy, snake_case field names map directly to database columns.

Frequently asked questions

How do I convert an entire JSON object's keys from camelCase to snake_case?

In Python, use a library like 'humps': import humps; humps.decamelize({'firstName': 'Jan'}). In Node.js, use 'snakecase-keys': const snakecaseKeys = require('snakecase-keys'); snakecaseKeys({ firstName: 'Jan' }). For a one-off check, convert each key with this tool.

Is 'myID' converted to 'my_id' or 'my_i_d'?

The tool treats a run of uppercase letters as a single word: 'myID' → tokens ['my', 'id'] → 'my_id'. If your input uses 'myId' (only the first letter capitalised), it also correctly produces 'my_id'.