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Snake case (sometimes stylizedautologically assnake_case) is thenaming convention in which each space is replaced with anunderscore (_) character, and words are written inall lower case. It is a commonly used naming convention incomputing, for example forvariable andsubroutine names, and forfilenames. One study has found that readers can recognize snake case values more quickly thancamel case. However, "subjects were trained mainly in the underscore style", so the possibility of bias cannot be eliminated.^[1]

A variation isscreaming snake case, where words are written inall caps (stylized as SCREAMING_SNAKE_CASE).^[2] This convention is used forconstants in programming languages likeC/C++,Python,Java,PHP, as well as forenvironment variables.

The use of underscores as word separators dates back to the late 1960s. It is particularly associated withC, is found inThe C Programming Language (1978), and contrasted with pascal case (a type ofcamel case). However, the convention traditionally had no specific name: thePython programming language style guide refers to it simply as "lower_case_with_underscores".^[3]

WithinUsenet the term snake_case was first seen in theRuby community in 2004,^[4] used by Gavin Kistner, writing:

BTW...what *do* you call that naming style? snake_case? That's what I'll call it until someone corrects me.

As of 2015^[update], names for other delimiter-separatednaming conventions for multiple-word identifiers have not been standardized, although some terms have increasing levels of usage, such as lisp-case, kebab-case, SCREAMING_SNAKE_CASE, and more.^[5][6][7]

The following programming languages use snake case by convention:

• ABAP^[8]
• Ada, with initial letters also capitalized^[9]
• C++ Standard Library andBoost for symbols.^[10]C++ does not have a widely agreed-upon naming convention for classes and functions by its wider community.
• C, for some type names in the standard library, but not for function names.
• Eiffel, for class and feature names^[11]
• Elixir, for atom, variable, and function names^[12]
• Erlang, for function names^[13]
• GDScript, for variable and function names^[14]
• Java uses SCREAMING_SNAKE_CASE for static final constants and enum values.^[15]
• Kotlin uses SCREAMING_SNAKE_CASE for constants and enum values^[16]
• Magik
• OCaml, for value, type, and module names^[17]
• Perl, for lexical variables and subroutines^[18]
• Oracle SQL andPL/SQL,^[19] for all unquoted identifiers (tables, columns, indexes, constraints, PL/SQL variables, constants, procedures/functions, triggers,...), although not official by Oracle itself, still recommended by the majority of known "influencers" and used throughout the official Oracle documentation
  • All unquoted snake_case identifiers are actually internally represented as SCREAMING_SNAKE_CASE identifiers.
• Prolog, for both atoms (predicate names, function names, and constants) and variables^[20]
• Python, for variable names, function names, method names, and module or package (i.e. file) names^[3]
• PHP uses SCREAMING_SNAKE_CASE for class constants
• PL/I^[21]
• R, for variable names, function names, and argument names, especially in the tidyverse style^[22]
• Ruby, for variable and method names^[23]
• Rust, for variable names, function names, method names, module names, and macros^[24]
• Tcl
• Terraform (software), for resources and variables^[25]
• Zig, for variables^[26]

• Camel case, more common inJava andC#
• Kebab case, more common inLISP
• Naming convention (programming)

• Snake case converter

• Capitalization
• Naming conventions
• Typography
• Source code
• Metaphors referring to snakes

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