toktok
A fast, exact BPE tokenizer for OpenAI encodings — Rust core, Python bindings. Token ids are byte-identical to tiktoken.
| encoder | throughput | CPU per MB | p99 latency | |
|---|---|---|---|---|
| toktok | Rust | 99.6 MB/s | 0.0117 s | 11.7 µs |
| bpe-openai | Rust | 30.2 | — | 42.6 µs |
| tiktoken-rs | Rust | 7.4 | — | 164.3 µs |
| tiktoken | Python | 16.2 | 0.0598 s | 156.3 µs |
The Pile, 25 MB, cl100k_base, single thread on a GitHub runner. Every encoder's ids are verified identical before timing. Full tables, memory figures and method: docs/BENCHMARKS.md.
Encodings: cl100k_base (GPT-3.5/GPT-4), o200k_base (GPT-4o),
o200k_harmony (GPT-OSS). They are compiled into the binary — no data files, no
downloads, no runtime dependencies.
Python
uv add toktok-rs # or: pip install toktok-rs
One function. Give it your texts and an encoding, get a token count per text:
import toktok
toktok.batch_count(["hello world", "how many tokens is this?"])
# [2, 6]
toktok.batch_count(docs, "gpt-4o") # model names work too
toktok.batch_count(docs, "cl100k_base", threads=4) # 0 = every core (default)
toktok.batch_count(["a<|endoftext|>b"], with_special=True) # [3]
batch_count(texts, encoding="cl100k_base", threads=0, with_special=False)
Returns list[int] — one count per text, in the order given.
| parameter | default | what it does |
|---|---|---|
texts |
— | any iterable of str. An empty iterable returns []; an empty string counts as 0. |
encoding |
"cl100k_base" |
which tokenizer to count with. Takes an encoding name — cl100k_base, o200k_base, o200k_harmony — or a model name, which resolves to that model's encoding: gpt-4o, gpt-4, gpt-3.5-turbo, o1, o3, text-embedding-3-small, openai/gpt-oss-20b. An org prefix is stripped, so HF-style ids work. Anything unrecognized raises KeyError. |
threads |
0 |
worker threads. 0 uses every core; 1 counts on the calling thread; any other number caps the pool. Counting releases the GIL, so this scales — including on free-threaded builds. Threads are only worth it for large batches; for a handful of short strings the pool costs more than it saves. |
with_special |
False |
how to treat special-token strings. False counts <|endoftext|> as the ordinary text it looks like (7 tokens); True counts it as the single special token it is (1). Use True when your text already contains rendered chat/control markup and you want the count the model will see. |
Ids are never built: one scratch buffer per thread is reused across texts, so a batch of any size allocates O(threads), not O(tokens).
Wheels cover CPython 3.11–3.14 plus free-threaded 3.14t, on Linux (x86_64, aarch64), macOS and Windows.
Need ids, decoding or offsets? toktok._encoding(name) returns the full
tokenizer — see docs/PYTHON.md.
Rust
cargo add toktok-rs # the crate is toktok-rs, the library is toktok
let tok = toktok::Tokenizer::builtin("cl100k_base")?; // nothing to download
let ids = tok.encode(b"hello world");
let text = tok.decode(&ids); // lossless, even on invalid UTF-8
let n = tok.count(b"how many tokens is this?");
// batch APIs are parallel; 0 threads means every core
let docs: Vec<&[u8]> = vec![b"first", b"second"];
let counts = tok.count_batch(&docs, 0, false); // no ids materialized
let batches = tok.encode_batch(&docs, 0, false);
let (ids, spans) = tok.encode_with_offsets(b"per-token byte spans");
Every batch method takes the same two knobs as the Python API:
| argument | meaning |
|---|---|
threads: usize |
0 uses every core; 1 runs on the calling thread; anything else caps the pool. |
with_special: bool |
false counts/encodes special strings as ordinary text; true maps them to their single special id. |
Tokenizer is Send + Sync — load it once and share it. Full API on
docs.rs/toktok-rs.
Cargo features
| feature | default | what it does |
|---|---|---|
embedded-data |
on | compiles the vocabularies into the binary (~4 MB of .rodata), so Tokenizer::builtin() needs no files at runtime. Turn it off (default-features = false) to drop them and load from a directory with Tokenizer::load_dir(dir, name) instead. |
More
- docs/BENCHMARKS.md — full results, memory and latency profile, how to reproduce
- docs/PYTHON.md — the tokenizer behind
batch_count - docs/DEVELOPMENT.md — layout, tests, how it's fast
- RELEASING.md —
scripts/release.sh patch|minor|major|X.Y.Z, and the registry setup
License
MIT — see LICENSE. Ported from quicktok (MIT); vocabulary data derives from tiktoken (MIT). See NOTICE.
Metadata
Release files for toktok-rs 0.1.1
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | |
|---|---|---|---|
| toktok_rs-0.1.1.tar.gz | 2.2 MB | Details |
Built distributions (wheels)
| File | Reset | |||
|---|---|---|---|---|
| toktok_rs-0.1.1-cp314-cp314t-win_amd64.whl | CPython 3.14 | CPython 3.14 free-threading | Windows x86-64 | Details |
| toktok_rs-0.1.1-cp314-cp314t-manylinux_2_28_x86_64.whl | CPython 3.14 | CPython 3.14 free-threading | Linux glibc 2.28+ x86-64 | Details |
| toktok_rs-0.1.1-cp314-cp314t-manylinux_2_28_aarch64.whl | CPython 3.14 | CPython 3.14 free-threading | Linux glibc 2.28+ ARM64 | Details |
| toktok_rs-0.1.1-cp314-cp314t-macosx_10_12_x86_64.macosx_11_0_arm64.macosx_10_12_universal2.whl | CPython 3.14 | CPython 3.14 free-threading | macOS 11.0+ ARM64, macOS 10.12+ universal2 (ARM64, x86-64), macOS 10.12+ x86-64 | Details |
| toktok_rs-0.1.1-cp311-abi3-win_amd64.whl | CPython 3.11 | abi3 | Windows x86-64 | Details |
| toktok_rs-0.1.1-cp311-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl | CPython 3.11 | abi3 | Linux glibc 2.17+ x86-64 | Details |
| toktok_rs-0.1.1-cp311-abi3-manylinux_2_17_aarch64.manylinux2014_aarch64.whl | CPython 3.11 | abi3 | Linux glibc 2.17+ ARM64 | Details |
| toktok_rs-0.1.1-cp311-abi3-macosx_10_12_x86_64.macosx_11_0_arm64.macosx_10_12_universal2.whl | CPython 3.11 | abi3 | macOS 10.12+ x86-64, macOS 10.12+ universal2 (ARM64, x86-64), macOS 11.0+ ARM64 | Details |
Total release size: 27.4 MB
Release files / toktok_rs-0.1.1.tar.gz
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