tiktoken

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The fastest Rust BPE tokenizer. Compatible with OpenAI tiktoken and supports all mainstream LLM tokenizers — OpenAI, Llama 3, DeepSeek, Qwen, and Mistral.

Features

• Multi-provider: 9 encodings across 5 vendors (OpenAI, Meta, DeepSeek, Alibaba, Mistral)
• Fast: arena-based vocabulary, heap-accelerated BPE merge, DFA regex
• Parallel encoding: optional rayon-based multi-threaded encoding for large texts
• Pricing: cost estimation for 57 models across 7 providers
• Compact: ruzstd-compressed vocabulary data embedded at compile time
• Zero-alloc counting: count() path avoids token vector allocation

Performance

All benchmarks on Apple M4 Mac mini, single-threaded. Token output verified identical across all three implementations.

cl100k_base encode

o200k_base encode

Benchmark source: benches/. Reproducible via cargo bench.

Installation

[dependencies]
tiktoken = "3"

# optional: multi-threaded encoding for large texts
tiktoken = { version = "3", features = ["parallel"] }

Quick Start

// by encoding name
let enc = tiktoken::get_encoding("cl100k_base").unwrap();
let tokens = enc.encode("hello world");
let text = enc.decode_to_string(&tokens).unwrap();
assert_eq!(text, "hello world");

// by model name — works across all providers
let enc = tiktoken::encoding_for_model("gpt-4o").unwrap();
let count = enc.count("hello world"); // zero-alloc fast path

let enc = tiktoken::encoding_for_model("llama-3.1-70b").unwrap();
let enc = tiktoken::encoding_for_model("deepseek-v3").unwrap();
let enc = tiktoken::encoding_for_model("qwen2.5-72b").unwrap();

Supported Encodings

API

Encode / decode

let enc = tiktoken::get_encoding("cl100k_base").unwrap();

let tokens = enc.encode("hello world");           // Vec<u32>
let text = enc.decode_to_string(&tokens).unwrap(); // String
let bytes = enc.decode(&tokens);                   // Vec<u8>

Special tokens

let enc = tiktoken::get_encoding("cl100k_base").unwrap();
let tokens = enc.encode_with_special_tokens("hello<|endoftext|>world");
// tokens will include the special token id for <|endoftext|>

Count tokens

let enc = tiktoken::get_encoding("o200k_base").unwrap();
let count = enc.count("The quick brown fox jumps over the lazy dog.");
// faster than encode().len() -- no token vector allocated

// count with special token recognition
let count = enc.count_with_special_tokens("hello<|endoftext|>world");

Parallel encoding

// requires `parallel` feature
let enc = tiktoken::get_encoding("cl100k_base").unwrap();
let tokens = enc.encode_parallel("...very long text...");
// identical output, uses rayon for texts >= 4KB

Cost estimation

use tiktoken::pricing;

// quick estimate
let cost = pricing::estimate_cost("gpt-4o", 1_000_000, 500_000).unwrap();

// with prompt caching
let model = pricing::get_model("claude-opus-4").unwrap();
let cost = model.estimate_cost_with_cache(500_000, 500_000, 200_000);

// list all models for a provider
let models = pricing::models_by_provider(pricing::Provider::DeepSeek);

Supports 57 models across OpenAI, Anthropic, Google, Meta, DeepSeek, Alibaba, and Mistral.

WebAssembly

Available as @goliapkg/tiktoken-wasm on npm.

npm install @goliapkg/tiktoken-wasm

import init, { getEncoding, encodingForModel, estimateCost } from '@goliapkg/tiktoken-wasm'

await init()

const enc = getEncoding('cl100k_base')
const tokens = enc.encode('hello world')    // Uint32Array
const text = enc.decode(tokens)             // "hello world"
const count = enc.count('hello world')      // 2

enc.free() // release WASM memory when done

See examples/react-app for a complete demo.

# requires wasm-pack: cargo install wasm-pack
cd tiktoken-wasm
wasm-pack build --target web --release

License

MIT

Third-party vocabulary data licenses: see LICENSE-3RD-PARTY.