vimspell - the rust crate.

The same great spell checking you love from Vim, but 3 times faster as a 100% safe Rust crate.

Fast spell checking using Vim's .spl dictionary files.

Features

• Fast: More than 3 times faster than C implementation in neovim.
• Drop-in Vim compatibility: Uses the same .spl files as Vim (format version 2)
• Smart suggestions: Edit distance + phonetic similarity (SAL) + character similarity (MAP)
• Regional variants: Filter by region (US/UK English, etc.)
• User dictionaries: Add custom words or ban incorrect ones at runtime
• Pure Safe Rust: No C bindings, no unsafe code, single common dependency (hashbrown)

Quick Start

use vimspell::Dictionary;

// Load a dictionary
let bytes = std::fs::read("en.utf-8.spl").unwrap();
let dict = Dictionary::parse(&bytes).unwrap();

// Check a word
assert!(dict.accepts_word("hello"));

// Get suggestions for typos (top 25, max score 350)
for (word, score) in dict.suggestions("speling", 25, 350) {
    println!("{}: {}", word, score);
}

// Scan a document
let text = "This is a sampel text with mistakse.";
for range in dict.spell_check(text) {
    println!("Typo: {}", &text[range]);
}

Getting Dictionary Files

Download pre-built .spl files from nlugg mirror for vim.

# English
curl -O ftp://ftp.nluug.nl/pub/vim/runtime/spell/en.utf-8.spl
# German
curl -O ftp://ftp.nlugg.nl/pub/vim/runtime/spell/de.utf-8.spl
# Spanish
curl -O ftp://ftp.nlugg.nl/pub/vim/runtime/spell/es.utf-8.spl

Or create your own with Neovim's :mkspell command.

Usage Examples

Custom User Dictionary

let mut dict = Dictionary::parse(&bytes).unwrap();

// Add technical terms
dict.insert_accepted_word("rustdoc");
dict.insert_accepted_word("async");

// Ban common mistakes
dict.insert_banned_word("alot");
dict.insert_banned_word("irregardless");

Regional Preferences

// Set to US English
dict.set_region(b"us");

// Or UK English
dict.set_region(b"gb");

// Accept all regions
dict.clear_region();

Tuning Suggestions

// Fewer results with a tighter score threshold for speed
let fast = dict.suggestions("recieve", 5, 200);

// More results with a looser threshold
let thorough = dict.suggestions("recieve", 25, 350);

for (word, score) in &thorough {
    println!("{}: {}", word, score);
}

Limitations

• Only supports VIMspell format version 2 (the current standard since 2006)
• For no english dictionaries:
  • Affix rules (prefixes/suffixes) are used for word checking but not for generating suggestions. Languages that rely heavily on affixes may produce fewer suggestion candidates.
  • Compound word validation parses nobreak, CHECKDUP, CHECKREP, CHECKCASE, and CHECKTRIPLE flags but does not enforce them. Compound checking still works via compound rules and patterns, but these additional constraints are ignored.
  • External sound folding files (SUG) not support.
  • Limited testing on non-English languages.

Acknowledgments

Spell checking algorithm ported from Neovim.