Skip to content

The code for our newly accepted paper in Pattern Recognition 2020: "U^2-Net: Going Deeper with Nested U-Structure for Salient Object Detection."


Notifications You must be signed in to change notification settings


Repository files navigation

U2-Net: U Square Net

This is the official repo for our paper U2-Net(U square net) published in Pattern Recognition 2020:

Xuebin Qin, Zichen Zhang, Chenyang Huang, Masood Dehghan, Osmar R. Zaiane and Martin Jagersand

Contact: xuebin[at]ualberta[dot]ca

Updates !!!

** (2022-Aug.-24) ** We are glad to announce that our U2-Net published in Pattern Recognition has been awarded the 2020 Pattern Recognition BEST PAPER AWARD !!! u2net-best-paper

** (2022-Aug.-17) ** Our U2-Net models are now available on PlayTorch, where you can build your own demo and run it on your Android/iOS phone. Try out this demo on PlayTorch Demo and bring your ideas about U2-Net to truth in minutes!

** (2022-Jul.-5)** Our new work **Highly Accurate Dichotomous Image Segmentation (DIS) Project Page, Github is accepted by ECCV 2022. Our code and dataset will be released before July 17th, 2022. Please be aware of our updates. ship-demo bg-removal view-move motor-demo

** (2022-Jun.-3)** Thank Adir Kol for sharing the iOS App 3D Photo Creator based on our U2-Net. portrait-ios-app

** (2022-Mar.-31)** Thank [Hikaru Tsuyumine] for implementing the iOS App Portrait Drawing based on our U2-Net portrait generation model. portrait-ios-app

** (2022-Apr.-12)** Thank Kevin Shah for providing us a great iOS App Lensto, (Demo Video), based on U2-Net. lensto

** (2022-Mar.-31)** Our U2-Net model is also integrated by for art design. hotpot

** (2022-Mar-19)** Thank Kikedao for providing a fantastic webapp Silueta based on U2-Net. More details can be found at silueta

** (2022-Mar-17)** Thank Ezaldeen Sahb for implementing the iOS library for image background removal based on U2-Net, which will greatly facilitate the developing of mobile apps. close-seg

** (2022-Mar-8)** Thank Levin Dabhi for training the amazing clothes segmentation U2-Net. close-seg

** (2022-Mar-3)** Thank Renato Violin for providing an awesome webapp for image background removal and replacement based on our U2-Net. bg-rm-aug

(2021-Dec-21) This blog clearly describes the way of converting U2-Net to CoreML and running it on iphone.

(2021-Nov-28) Interesting Sky Segmentation models developed by xiongzhu using U2-Net.


(2021-Nov-28) Awesome image editing app Pixelmator pro uses U2-Net as one of its background removal models.


(2021-Aug-24) We played a bit more about fusing the orignal image and the generated portraits to composite different styles. You can
(1) Download this repo by

git clone

(2) Download the u2net_portrait.pth from GoogleDrive or Baidu Pan(提取码:chgd)model and put it into the directory: ./saved_models/u2net_portrait/,
(3) run the code by command

python -s 20 -a 0.5

,where -s indicates the sigma of gaussian function for blurring the orignal image and -a denotes the alpha weights of the orignal image when fusing them.


(2021-July-16) A new background removal webapp developed by Изатоп Василий.


(2021-May-26) Thank Dang Quoc Quy for his Art Transfer APP built upon U2-Net.

(2021-May-5) Thank AK391 for sharing his Gradio Web Demo of U2-Net.


(2021-Apr-29) Thanks Jonathan Benavides Vallejo for releasing his App LensOCR: Extract Text & Image, which uses U2-Net for extracting the image foreground.


(2021-Apr-18) Thanks Andrea Scuderi for releasing his App Clipping Camera, which is an U2-Net driven realtime camera app and "is able to detect relevant object from the scene and clip them to apply fancy filters".

Clipping Camera APP

(2021-Mar-17) Dennis Bappert re-trained the U2-Net model for human portrait matting. The results look very promising and he also provided the details of the training process and data generation(and augmentation) strategy, which are inspiring.

(2021-Mar-11) Dr. Tim developed a video version rembg for removing video backgrounds using U2-Net. The awesome demo results can be found on YouTube.

(2021-Mar-02) We found some other interesting applications of our U2-Net including MOJO CUT, Real-Time Background Removal on Iphone, Video Background Removal, Another Online Portrait Generation Demo on AWS, AI Scissor.

(2021-Feb-15) We just released an online demo for the portrait generation. Please feel free to give it a try and provide any suggestions or comments.

(2021-Feb-06) Recently, some people asked the problem of using U2-Net for human segmentation, so we trained another example model for human segemntation based on Supervisely Person Dataset.

(1) To run the human segmentation model, please first downlowd the u2net_human_seg.pth model weights into ./saved_models/u2net_human_seg/.
(2) Prepare the to-be-segmented images into the corresponding directory, e.g. ./test_data/test_human_images/.
(3) Run the inference by command: python and the results will be output into the corresponding dirctory, e.g. ./test_data/u2net_test_human_images_results/
Notes: Due to the labeling accuracy of the Supervisely Person Dataset, the human segmentation model (u2net_human_seg.pth) here won't give you hair-level accuracy. But it should be more robust than u2net trained with DUTS-TR dataset on general human segmentation task. It can be used for human portrait segmentation, human body segmentation, etc.

Human Image Segmentation
Human Video Human Video Results

(2020-Dec-28) Some interesting applications and useful tools based on U2-Net:
(1) Xiaolong Liu developed several very interesting applications based on U2-Net including Human Portrait Drawing(As far as I know, Xiaolong is the first one who uses U2-Net for portrait generation), image matting and so on.
(2) Vladimir Seregin developed an interesting tool, NN based lineart, for comparing the portrait results of U2-Net and that of another popular model, ArtLine, developed by Vijish Madhavan.
(3) Daniel Gatis built a python tool, Rembg, for image backgrounds removal based on U2-Net. I think this tool will greatly facilitate the application of U2-Net in different fields.

(2020-Nov-21) Recently, we found an interesting application of U2-Net for human portrait drawing. Therefore, we trained another model for this task based on the APDrawingGAN dataset.

Sample Results: Kids

Sample Results: Ladies

Sample Results: Men

Usage for portrait generation

  1. Clone this repo to local
git clone
  1. Download the u2net_portrait.pth from GoogleDrive or Baidu Pan(提取码:chgd)model and put it into the directory: ./saved_models/u2net_portrait/.

  2. Run on the testing set.
    (1) Download the train and test set from APDrawingGAN. These images and their ground truth are stitched side-by-side (512x1024). You need to split each of these images into two 512x512 images and put them into ./test_data/test_portrait_images/portrait_im/. You can also download the split testing set on GoogleDrive.
    (2) Running the inference with command python will ouptut the results into ./test_data/test_portrait_images/portrait_results.

  3. Run on your own dataset.
    (1) Prepare your images and put them into ./test_data/test_portrait_images/your_portrait_im/. To obtain enough details of the protrait, human head region in the input image should be close to or larger than 512x512. The head background should be relatively clear.
    (2) Run the prediction by command python will outputs the results to ./test_data/test_portrait_images/your_portrait_results/.
    (3) The difference between python and python is that we added a simple face detection step before the portrait generation in Because the testing set of APDrawingGAN are normalized and cropped to 512x512 for including only heads of humans, while our own dataset may varies with different resolutions and contents. Therefore, the code python will detect the biggest face from the given image and then crop, pad and resize the ROI to 512x512 for feeding to the network. The following figure shows how to take your own photos for generating high quality portraits.

(2020-Sep-13) Our U2-Net based model is the 6th in MICCAI 2020 Thyroid Nodule Segmentation Challenge.

(2020-May-18) The official paper of our U2-Net (U square net) (PDF in elsevier(free until July 5 2020), PDF in arxiv) is now available. If you are not able to access that, please feel free to drop me an email.

(2020-May-16) We fixed the upsampling issue of the network. Now, the model should be able to handle arbitrary input size. (Tips: This modification is to facilitate the retraining of U2-Net on your own datasets. When using our pre-trained model on SOD datasets, please keep the input size as 320x320 to guarantee the performance.)

(2020-May-16) We highly appreciate Cyril Diagne for building this fantastic AR project: AR Copy and Paste using our U2-Net (Qin et al, PR 2020) and BASNet(Qin et al, CVPR 2019). The demo video in twitter has achieved over 5M views, which is phenomenal and shows us more application possibilities of SOD.

U2-Net Results (176.3 MB)

U<sup>2</sup>-Net Results

Our previous work: BASNet (CVPR 2019)

Required libraries

Python 3.6
numpy 1.15.2
scikit-image 0.14.0
python-opencv PIL 5.2.0
PyTorch 0.4.0
torchvision 0.2.1

Usage for salient object detection

  1. Clone this repo
git clone
  1. Download the pre-trained model u2net.pth (176.3 MB) from GoogleDrive or Baidu Pan 提取码: pf9k or u2netp.pth (4.7 MB) from GoogleDrive or Baidu Pan 提取码: 8xsi and put it into the dirctory './saved_models/u2net/' and './saved_models/u2netp/'

  2. Cd to the directory 'U-2-Net', run the train or inference process by command: python or python respectively. The 'model_name' in both files can be changed to 'u2net' or 'u2netp' for using different models.

We also provide the predicted saliency maps (u2net results,u2netp results) for datasets SOD, ECSSD, DUT-OMRON, PASCAL-S, HKU-IS and DUTS-TE.

U2-Net Architecture

U<sup>2</sup>-Net architecture

Quantitative Comparison

Quantitative Comparison

Quantitative Comparison

Qualitative Comparison

Qualitative Comparison


title = {U2-Net: Going Deeper with Nested U-Structure for Salient Object Detection},
author = {Qin, Xuebin and Zhang, Zichen and Huang, Chenyang and Dehghan, Masood and Zaiane, Osmar and Jagersand, Martin},
journal = {Pattern Recognition},
volume = {106},
pages = {107404},
year = {2020}


The code for our newly accepted paper in Pattern Recognition 2020: "U^2-Net: Going Deeper with Nested U-Structure for Salient Object Detection."








No releases published


No packages published