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unicorn/filename-case Style

What it does

Enforces a consistent case style for filenames to improve project organization and maintainability. By default, kebab-case is enforced, but other styles can be configured.

Files named index.js, index.ts, etc. are exempt from this rule as they cannot reliably be renamed to other casings (mainly just a problem with PascalCase).

Why is this bad?

Inconsistent file naming conventions make it harder to locate files, navigate projects, and enforce consistency across a codebase. Standardizing naming conventions improves readability, reduces cognitive overhead, and aligns with best practices in large-scale development.

Examples

Examples of correct filenames for each case:

kebabCase

• some-file-name.js
• some-file-name.test.js
• some-file-name.test-utils.js

camelCase

• someFileName.js
• someFileName.test.js
• someFileName.testUtils.js

snakeCase

• some_file_name.js
• some_file_name.test.js
• some_file_name.test_utils.js

pascalCase

• SomeFileName.js
• SomeFileName.Test.js
• SomeFileName.TestUtils.js

lowercase

Only rejects uppercase letters; separators are allowed.

• somefilename.js
• some-file-name.js
• some_file_name.js

screamingSnakeCase

• SOME_FILE_NAME.js
• SOME_FILE_NAME.TEST.js
• SOME_FILE_NAME.TEST_UTILS.js

Configuration

This rule accepts a configuration object with the following properties:

case

type: "kebabCase" | "camelCase" | "snakeCase" | "pascalCase" | "lowercase" | "screamingSnakeCase"

default: null

The case style to enforce for filenames.

You can set the case option like this:

{
  "unicorn/filename-case": [
    "error",
    {
      "case": "kebabCase"
    }
  ]
}

cases

type: object

default: null

The case style(s) to allow/enforce for filenames. true means the case style is allowed, false means it is banned.

You can set the cases option like this:

{
  "unicorn/filename-case": [
    "error",
    {
      "cases": {
        "camelCase": true,
        "pascalCase": true
      }
    }
  ]
}

cases.camelCase

type: boolean

default: false

Whether camel case is allowed, e.g. someFileName.js.

cases.kebabCase

type: boolean

default: false

Whether kebab case is allowed, e.g. some-file-name.js.

cases.lowercase

type: boolean

default: false

Whether lowercase is allowed, e.g. somefilename.js.

cases.pascalCase

type: boolean

default: false

Whether pascal case is allowed, e.g. SomeFileName.js.

cases.screamingSnakeCase

type: boolean

default: false

Whether screaming snake case is allowed, e.g. SOME_FILE_NAME.js.

cases.snakeCase

type: boolean

default: false

Whether snake case is allowed, e.g. some_file_name.js.

ignore

type: string[]

An array of regular expression patterns for filenames to ignore.

You can set the ignore option like this:

{
  "unicorn/filename-case": [
    "error",
    {
      "ignore": ["^foo.*$"]
    }
  ]
}

multipleFileExtensions

type: boolean

default: true

Whether to treat additional, .-separated parts of a filename as parts of the extension rather than parts of the filename.

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
  "rules": {
    "unicorn/filename-case": "error"
  }
}

Config (oxlint.config.ts)

import { defineConfig } from "oxlint";

export default defineConfig({
  rules: {
    "unicorn/filename-case": "error",
  },
});

CLI

oxlint --deny unicorn/filename-case

Version

This rule was added in v0.0.14.

References

• Rule Source
• Upstream rule docs
• Open rule in Oxc Playground