WeMM-Embedding: WeChat Multi-Modal Embedding

WeMM-Embedding is a family of universal multimodal embedding models developed by the WeChat Vision team. It provides unified representations for text, images, videos, visual documents, and interleaved multimodal inputs, achieving state-of-the-art performance across multiple benchmarks covering diverse tasks and domains.

Model Zoo

All models support text, images, videos, visual documents, and interleaved multimodal inputs. Embeddings are obtained from the last-layer hidden state at the dedicated <embedding> token position, followed by L2 normalization. Audio input is not currently supported.

Installation

pip install -r requirements.txt

Transformers

We recommend using transformers==5.2.0 for inference and reproducibility, as newer versions may differ in preprocessing behavior.

python examples/transformers_inference.py \
  --model /path/to/WeMM-Embedding-2B \
  --image /path/to/image.jpg \
  --video /path/to/video.mp4 \
  --dimension 2048

The example produces independent text, image, and video embeddings. Omit --dimension for the full embedding dimension.

Sentence Transformers

python examples/sentence_transformers_inference.py \
  --model /path/to/WeMM-Embedding-2B \
  --image /path/to/image.jpg \
  --video /path/to/video.mp4 \
  --dimension 2048

SentenceTransformer loads the model directly, so a Hugging Face model id such as tencent/WeMM-Embedding-2B also works in place of a local path. Text, image, and video inputs go through SentenceTransformer.encode(), and MRL is selected with --dimension.

Serving

Tested versions: vLLM 0.27.0 and SGLang 0.5.9.

vLLM:

MODEL_PATH=/path/to/WeMM-Embedding-2B
vllm serve "$MODEL_PATH" \
  --runner pooling \
  --chat-template "$MODEL_PATH/embedding_chat_template.jinja"

SGLang:

MODEL_PATH=/path/to/WeMM-Embedding-2B
python scripts/patch_sglang_video.py
python -m sglang.launch_server \
  --model-path "$MODEL_PATH" \
  --is-embedding \
  --enable-precise-embedding-interpolation

Equivalent one-command wrappers are available in scripts/serve_vllm.sh and scripts/serve_sglang.sh.

Matryoshka Embeddings

For a supported dimension d, truncate the full embedding and normalize it again:

embedding = torch.nn.functional.normalize(embedding[..., :d], dim=-1)

On MMEB-v2, the 2B model at 256 dimensions retains 98.7% of its full-dimensional image and video performance.

Evaluation

MMEB-v2

Results on 78 datasets. Image and video tasks use Hit@1, while visual-document tasks use NDCG@5. Higher is better.

MMEB-v3

Results on 190 tasks. V3-All includes the 78 MMEB-v2 tasks, 53 text tasks, 47 agent tasks, 11 audio tasks, and MCMR.

Text results use NDCG@5; agent, MCMR, and audio results use Hit@1.

cd mmeb_v3_eval
DATA_ROOT=/path/to/MMEB-V3 bash scripts/download_data.sh
MODEL_PATH=/path/to/WeMM-Embedding-2B DATA_BASEDIR=/path/to/MMEB-V3 \
OUTPUT_DIR=exps/wemm_embedding bash scripts/run_eval.sh

Citation

@article{wemm-embedding,
      title={WeMM-Embedding: WeChat Multi-Modal Embedding Technical Report}, 
      author={Junjie Zhou and Ke Mei and Lei Li and Tianyi Wang and Fengyun Rao and Jing Lyu},
      year={2026},
      eprint={2608.24053},
      archivePrefix={arXiv},
      primaryClass={cs.CV},
      url={https://arxiv.org/abs/2608.24053}, 
}

License

Unless otherwise noted, Tencent-authored code in this repository is released under the Apache License 2.0.