An Emacs major mode for editing Nix expressions, powered by the built-in tree-sitter support in Emacs 29+ and the community-maintained Nix tree-sitter grammar.

Features:

• Syntax highlighting for all Nix language constructs
• Semantic distinctions (variables vs properties, function calls vs definitions)
• 100% tree-sitter-nix grammar coverage
• Comprehensive tests

Requirements: Emacs 29+ with tree-sitter support, 30.x includes more improvements.

nix-ts-mode provides comprehensive syntax highlighting and indentation for Nix files. After installing, enable the mode for Nix files like so:

(require 'nix-ts-mode)
(add-to-list 'auto-mode-alist '("\\.nix\\'" . nix-ts-mode))

Or with use-package:

(use-package nix-ts-mode
 :mode "\\.nix\\'")

For the best syntax highlighting experience with the widest selection of font-lock faces, set the font-lock level to 4 (maximum):

;; Add to your init.el before loading nix-ts-mode
(setq treesit-font-lock-level 4)

This enables:

• Fine-grained semantic distinctions (variables vs properties)
• Function parameter highlighting
• Punctuation and bracket highlighting
• Complete visual clarity
• below is a list of what is included at each level
• test/highlighting-example.nix can be use to see the effects of the levels.

• comment
• builtin
• constant

• string
• path
• uri

• number
• operator
• definition
• function-call
• keyword

• parameter
• property
• variable
• bracket
• delimiter
• ellipses
• punctuation
• **paren-base** (override)
• **parameter-atpattern** (override)
• error