Convert any phrase into snake_case — all lowercase, words joined by underscores. Default identifier style for Python, Ruby, and most SQL columns.
User Profile Background Color → user_profile_background_color
snake_case is a naming convention where words are written in lowercase and joined by underscores. It's the official identifier style for Python (per PEP 8) and Ruby, and it's overwhelmingly the most common style for SQL column names across PostgreSQL, MySQL, and SQLite.
Compared to camelCase, snake_case is easier to read at a glance because the underscores act as visual separators, but it's slightly slower to type because every word break requires a dedicated keystroke. Languages and ecosystems pick one or the other and stick to it for consistency.
Per PEP 8, every Python variable, function parameter, and method name should be snake_case: user_id, compute_tax_rate, read_from_file. Class names are PascalCase; constants are CONSTANT_CASE.
Ruby methods, variables, and Rails model attributes are all snake_case. Database columns convert automatically to snake_case attribute names in ActiveRecord, so any deviation breaks the magic.
PostgreSQL, MySQL, and SQLite are all case-insensitive for unquoted identifiers, but snake_case is the de-facto standard. created_at, user_email, order_total.
snake_case is friendly for filenames and URL slugs that need underscores rather than dashes. (For URL slugs, kebab-case is more common — Google treats hyphens as word separators in URLs but underscores as connectors.)
While environment variables are conventionally CONSTANT_CASE, the underscore separator is the same. snake_case is one toUpperCase() away from a valid env var name.
It depends on your language and team conventions. Python, Ruby, and most databases prefer snake_case. JavaScript, Java, C#, Swift, and Kotlin prefer camelCase. The rule is to follow your language's official style guide and your team's existing code — never mix conventions inside one codebase.
Underscore-prefixed names like _private often signal "internal use only" in Python and Ruby. Double underscores (__name__) are reserved for language-defined identifiers. Our converter strips leading and trailing underscores from regular phrases — add them back manually if you need them.
Digits stay where they are: "version 2 alpha" → "version_2_alpha". A digit immediately after a letter is not separated unless the input has a space or punctuation between them.
The all-lowercase letters with underscore breaks visually resemble a snake slithering across the page. The name was popularised in the early Ruby community in the mid-2000s.