quicktok-v1 0.3.0

Fast exact BPE tokenizer for OpenAI and open-model encodings (cl100k, o200k, GPT-OSS, Llama-3, Qwen)

quicktok

A fast, exact BPE tokenizer for OpenAI and open-model encodings, written in C++. Token ids are byte-identical to tiktoken; encoding runs 2–3.5× faster than the fastest exact tokenizer we know of (bpe-openai) and 4–11× faster than tiktoken itself. See benchmarks.

• Exact — ids match tiktoken byte-for-byte; every benchmark is exactness-checked before timing.
• Drop-in — Python wheels with a tiktoken-style API, a stable C ABI, CMake support.
• Self-contained — C++20, no external dependencies; cl100k_base, o200k_base, o200k_harmony, Llama-3, and Qwen2.5/3 ship in the repo.
• Thread-safe — load once, call encode() from as many threads as you like.

Install

Python (the PyPI package is quicktok-v1; you still import quicktok):

pip install quicktok-v1

import quicktok
enc = quicktok.get_encoding("cl100k_base")        # or "o200k_base", "llama3"
ids = enc.encode("hello world")                   # == tiktoken.encode_ordinary
text = enc.decode(ids)
quicktok.encoding_for_model("gpt-4o").count("...")  # tiktoken-style model lookup

C++ — via CMake (find_package or FetchContent), or make install and pkg-config. There's also a stable C ABI (quicktok.h) for FFI from any language.

find_package(quicktok REQUIRED)
target_link_libraries(app PRIVATE quicktok::quicktok)

Build from source

git clone https://github.com/dmatth1/quicktok
cd quicktok
make            # builds build/libquicktok.{a, dylib/so}
make test       # verifies exact ids vs tiktoken (all encodings) + C ABI

#include <quicktok.hpp>

auto tok = quicktok::Tokenizer::load_dir("data");              // cl100k_base
auto gpt4o = quicktok::Tokenizer::load_dir("data", "o200k_base");

auto ids = tok.encode("Hello, quicktok! 日本語 🚀");  // std::vector<uint32_t>
std::string text = tok.decode(ids);                   // lossless round-trip
size_t n = tok.count("how many tokens is this?");
auto with_sp = tok.encode_with_special("a<|endoftext|>b");  // specials -> ids
auto batch = tok.encode_batch(texts);                       // parallel

The data files install to share/quicktok.

Benchmarks

Five encoders, same machine (Apple M1), single thread, every output verified token-for-token identical before timing. Three 25 MB corpora streamed from their real sources — The Pile (diverse), GitHub code, Common Crawl (multilingual) — across both common OpenAI encodings (throughput in MB/s):

cl100k_base (GPT-3.5 / GPT-4)

encoder	The Pile	Code	Common Crawl
quicktok	116.1	144.2	75.2
bpe-openai	36.5	41.6	29.2
tiktoken-rs	15.3	14.3	13.5
tiktoken (Python)	14.7	13.2	12.3
TokenDagger	11.5	12.0	11.2

o200k_base (GPT-4o)

encoder	The Pile	Code	Common Crawl
quicktok	100.6	117.1	59.2
bpe-openai	36.1	40.1	29.9
tiktoken-rs	23.1	20.9	17.9
tiktoken (Python)	21.6	19.3	16.3
TokenDagger	11.0	11.7	10.2

Reproduce these tables: make bench-compare — see bench/README.md.

Parallel / batch scaling (Apple M1, 8 threads)

Native encode_batch() (make bench), cl100k:

threads	MB/s	speedup
1	110	1.0×
2	210	1.9×
4	397	3.6×
8	706	6.4×

From Python (make bench-py), cl100k, 10 threads:

Python API	quicktok	tiktoken	speedup
single-thread	77 MB/s	15 MB/s	5.0×
encode_batch	550 MB/s	24 MB/s (batch)	24×

x86 cross-check (cl100k + o200k, The Pile / Code / Common Crawl)

Same encoders, corpora, and method on an x86 server (Intel Xeon @ 2.8 GHz, single thread, MB/s). quicktok is shown both as the native C++ kernel and as the Python wheel:

cl100k_base (GPT-3.5 / GPT-4)

encoder	The Pile	Code	Common Crawl
quicktok (native)	75.0	86.6	47.9
quicktok (Python)	42.5	47.4	29.6
bpe-openai	25.9	30.8	22.9
tiktoken-rs	11.1	10.2	11.1
tiktoken (Python)	10.2	9.1	9.5
TokenDagger	7.1	7.6	7.1

o200k_base (GPT-4o)

encoder	The Pile	Code	Common Crawl
quicktok (native)	60.9	69.5	37.3
quicktok (Python)	36.6	41.1	26.7
bpe-openai	24.4	28.9	23.9
tiktoken-rs	17.0	15.5	15.1
tiktoken (Python)	14.2	13.3	13.2
TokenDagger	6.6	7.3	6.2

Same ordering as the M1 tables, the Python wheel included. (One footnote: TokenDagger diverges from the other four by a single token on Pile/cl100k — a known TokenDagger edge case, not an encoder bug.)

vs llama.cpp (x86 server, Llama-3 vocab, FineWeb 15 MB)

Same Llama-3 128k vocab (ggml-vocab-llama-bpe.gguf), quicktok's kernel vs libllama's own llama_tokenize:

	MB/s	Mtok/s
quicktok (Llama-3)	~78	~17
llama.cpp	~5.4	~1.2

Token agreement is 99.9998% (3,274,274 of 3,274,281); the 7 differing tokens are a known tiktoken-rank vs HF-merges divergence on rare Cyrillic+symbol sequences, not an encoder bug. See Encodings.

Notes on fairness

Every reference is called through the same raw API its own benchmark uses (e.g. encode_ordinary, encode_via_backtracking) — no convenience-wrapper handicaps. TokenDagger's README claims 2–4× over tiktoken, but that's on Llama-4/Mistral vocabs on AMD EPYC; on cl100k/o200k here it lands around Python tiktoken's level.

How it's fast

Same algorithm as bpe-openai (exact backtracking BPE) — the speed is data-structure engineering:

• 2-byte trie — the longest-match walk reads 2 input bytes per single 8-byte slot load, with a zero-lookup direct table for CJK characters.
• Dense validity memos — merge-validity checks hit exactly-keyed caches (2 MB for 17-bit token ids, a second wide one for 200k-vocab ids; a bijective mixer means no aliasing, ever).
• Specialized pretokenizers — the fixed cl100k/o200k-family regexes are compiled by hand into SIMD scanners; no general regex engine anywhere.

API

namespace quicktok {
class Tokenizer {
    // encoding: "cl100k_base" (default), "o200k_base", "o200k_harmony", "llama3", "qwen3", "llama4"
    static Tokenizer load_dir(const std::string& dir, const std::string& encoding = "cl100k_base");

    std::vector<uint32_t> encode(std::string_view text) const;          // encode_ordinary semantics
    std::vector<uint32_t> encode_with_special(std::string_view) const;  // allowed_special="all"
    void encode(const uint8_t* text, size_t len, std::vector<uint32_t>& out) const;
    std::vector<std::vector<uint32_t>> encode_batch(const std::vector<std::string_view>&, unsigned threads = 0) const;
    size_t count(std::string_view text) const;

    std::string decode(const std::vector<uint32_t>& ids) const;         // handles special ids too
    void decode(const uint32_t* ids, size_t n, std::string& out) const;

    size_t vocab_size() const;
    const std::string& encoding() const;
};
}

• encode() is tiktoken's encode_ordinary (special tokens treated as plain text); encode_with_special() is tiktoken's encode(text, allowed_special="all"). Both byte-exact vs the reference, both tested.
• Any byte sequence is accepted; invalid UTF-8 round-trips through encode/decode unchanged.
• Python's encode_batch returns a flat uint32 token array plus int64 offsets (tokens[offsets[i]:offsets[i+1]] is document i, no per-document Python lists); count_batch(enc, texts) gives per-document counts.
• load* throws std::runtime_error on missing or corrupt data files. Nothing throws on the encode hot path (one exception: inputs over 4 GiB per call are rejected).
• A loaded Tokenizer is safe to share across threads — concurrent encode()/decode() is supported and tested.

Encodings

Five encodings ship in the repo, each byte-exact vs its reference:

name	model family	reference	notes
cl100k_base	GPT-3.5 / GPT-4	tiktoken	the default
o200k_base	GPT-4o	tiktoken	~85% of cl100k speed (2× vocab)
o200k_harmony	GPT-OSS (20b/120b)	tiktoken	same pattern + ranks as o200k_base, extra chat specials
llama3	Llama 3	Meta tiktoken-rank	full cl100k speed; see exactness note
qwen3	Qwen2.5 / Qwen3	HF tokenizers	cl100k speed; single-digit numbers

Load one by encoding name. The Python wheel bundles all the data files, so a name is all you need; in C++ you also point at the directory holding them (data/ in this repo, or wherever make install put them):

enc = quicktok.get_encoding("qwen3")                        # Python: data ships in the wheel

auto tok = quicktok::Tokenizer::load_dir("data", "qwen3");  // C++: same thing, explicit data dir

• Qwen2.5 / Qwen3 share one byte-level BPE; quicktok reproduces the Hugging Face tokenizer byte-for-byte. Apache-2.0; regenerate with tools/export_qwen.py --download.

• o200k_harmony is o200k_base plus the harmony chat specials (<|start|>, <|channel|>, <|return|>, …) — ordinary text encodes identically to o200k_base.

• Llama-3 reproduces Meta's original tiktoken-rank BPE byte-for-byte (Meta Llama 3 Community License, see NOTICE; regenerate with tools/export_llama3.py <tokenizer.json> data). Hugging Face / llama.cpp infer the same vocab from a merge list and agree on ~99.9998% of tokens — the rare differences are non-Latin+symbol sequences (e.g. Cyrillic next to €) where rank order and merge order pick different splits.

• Llama-4 uses the same pretokenizer as o200k_base, so the code path ships — but Meta's vocab is gated and not bundled. Export your own, then load it:

  python tools/export_llama4.py <tokenizer.model> data
  

  enc = quicktok.get_encoding("llama4", "data")
  

Notes

• Builds tune to the host CPU by default (-march=native); set CXXFLAGS_ARCH for portable binaries.

• The bundled Unicode table is pinned and version-stamped; python tools/export_unicode.py verify re-derives all 1.1 M codepoints against the live reference and diffs them — see data/uniclass.bin.meta.

• To regenerate the data files from the references:

  pip install tiktoken regex tokenizers
  python tools/export_fixtures.py        # cl100k/o200k/o200k_harmony from tiktoken
  python tools/export_qwen.py --download  # data/qwen3.vocab (Apache-2.0)
  python tools/export_unicode.py         # data/uniclass.bin + version stamp
  python tools/gen_vectors.py            # test vectors (tiktoken encodings)
  

License

MIT — see LICENSE.