UniTok

UniTok: A Unified Tokenizer
for Visual Generation and Understanding

Chuofan Ma1,2 · Yi Jiang2† · Junfeng Wu2,3 · Jihan Yang1

Xin Yu1 · Zehuan Yuan2* · Bingyue Peng2 · Xiaojuan Qi1†*

1HKU   2ByteDance   3HUST

†project lead   *corresponding author

[//]: # ()

This repo implements UniTok, a unified visual tokenizer well-suited for both generation and understanding tasks. It is compatiable with autoregressive generative models (e.g. LlamaGen), multimodal understanding models (e.g. LLaVA), and unified MLLMs (e.g. Chameleon and Liquid).

Built upon UniTok, we construct an MLLM capable of both multimodal generation and understanding with the Liquid framework, which sets a new state-of-the-art among unified autoregressive MLLMs.

News

2025-09-18: UniTok is accepted at NeurIPS 2025 as a spotlight.

2025-05-19: We find UniTok favors generation without classifier-free-guidance -- it reduces gFID (without cfg) from 14.6 to 2.51 on ImageNet 256x256 using LlamaGen-XXL as the generator. Please refer to the updated EVAL.md for more details.

2025-04-15: The gradio demo of UniTok MLLM is available on Huggingface now!

2025-04-02: A new checkpoint of UniTok is released, which has better downstream task performance by replacing the causal attention projection layer with full attention. The model weights of our unified MLLM are also available on Huggingface now!

2025-02-28: Paper, code, model, and project page for UniTok are all released.

Performance

Method

#Tokens

rFID ↓

Accuracy

VQVAE Model

VQ-GAN

256

4.98

--

RQ-VAE

256

1.30

--

VAR

680

0.90

--

CLIP Model

CLIP

256

--

76.2

SigLIP

256

--

80.5

ViTamin

256

--

81.2

Unified Model

TokenFlow †

680

1.37

--

VILA-U †

256

1.80

73.3

UniTok

256

0.41

70.8

UniTok †

256

0.38

78.6

† indicates the model uses pretrained CLIP weights for initialization. Although CLIP weight initialization boosts ImageNet zero-shot accuracy, we notice that random initialization leads to better downstream understanding performance. We thus release the model checkpoint of UniTok that is trained from scratch.

Model Weights

Usage

Requirements

• Python ≥ 3.10
• PyTorch ≥ 2.3.1

Installation

git clone https://github.com/FoundationVision/UniTok.git
cd UniTok
pip install -r requirements.txt

Inference

Please download the checkpoint and fill in the ckpt_path.

python inference.py \
    --ckpt_path /path/to/unitok_tokenizer.pth \
    --src_img /path/to/test_img --rec_img /path/to/rec_img

Training

• We train UniTok on DataComp-1B. Please follow the instructions to download and prepare the data.

• Download the models used for loss calculation and put them under ./external.

• Download the ImageNet validation set for zero-shot accuracy evaluation.

• Download the ImageNet 256$\times$256 reference batch for FID evaluation.

Configure nnodes, nproc_per_node, node_rank, master_addr, master_port in launch.sh and run:

bash launch.sh \
    --output_dir '/path/to/save/checkpoints/' \
    --train_data '/path/to/datacomp/shards/{00000000..00140146}.tar' \
    --imagenet_val '/path/to/imagenet_val/' \
    --fid_eval_src '/path/to/imagenet_reference_batch' \
    --fid_eval_dst '/path/to/save/imagenet_reconstructed_batch'

Note: For more hyper-parameter configurations, please check utils/config.py.

Unified MLLM

We show that UniTok significantly boosts the performance of unified MLLMs.

Visual Understanding Performance on VQA Benchmarks.

Visual Generation Performance on GenAI-Bench.

Method

Type

Count

Differ

Compare

Logical

Overall

Negate

Universal

Show-o

Discrete Diff.

0.70

0.62

0.71

0.51

0.65

0.60

VILA-U

Autoregressive

0.70

0.71

0.74

0.53

0.66

0.64

Liquid

Autoregressive

0.76

0.73

0.74

0.46

0.74

0.65

UniTok

Autoregressive

0.76

0.79

0.74

0.46

0.73

0.67

Please refer to EVAL.md for more details.

Evaluation

We also benchmark UniTok in terms of both understanding performance using the LLaVA framework and generation performance using the LLamaGen framework. Please refer to EVAL.md for more details.

Acknowledgement

UniTok is built upon the awesome works VAR, DataComp, Liquid, LLaVA, LlamaGen, and ViTamin.

LICENSE

This project is licensed under the MIT License - see the LICENSE file for details.

Citation

If you find this project useful, please consider citing:

@article{unitok,
  title={UniTok: A Unified Tokenizer for Visual Generation and Understanding},
  author={Ma, Chuofan and Jiang, Yi and Wu, Junfeng and Yang, Jihan and Yu, Xin and Yuan, Zehuan and Peng, Bingyue and Qi, Xiaojuan},
  journal={arXiv preprint arXiv:2502.20321},
  year={2025}
}