How background removal runs inside your browser
Why your photo never leaves your device, what happens on the first visit, and why some older devices get a simpler engine.
Most background removers upload your photo to a server, run a model there, and send the result back. CRD does the work on your own device. Here is how that works, and where its limits are.
The model
We use BiRefNet_lite, an open segmentation model released under the MIT licence. It is good at fine edges like hair and fur for its size. We run the ONNX version through transformers.js.
What happens on your first visit
- When you open the editor, your browser checks whether it supports WebGPU, the modern way for web pages to use your graphics chip.
- If it does, the model file downloads once. That is about 115 MB on most GPUs, or about 224 MB on GPUs without half precision support. Your browser caches it, so later visits skip this step.
- The model runs in a background worker, so the page stays responsive while it thinks.
What happens when you drop a photo
Your image is decoded in the browser. The model looks at a 1024 by 1024 version of it and predicts a mask: how much of each pixel belongs to the subject. We then scale that mask back up to your original size and apply it, so the download keeps your full resolution, up to 25 megapixels.
Nothing in that chain talks to our servers. The only network request is the one time model download.
Why it is free
Because your device does the work, each cutout costs us nothing to run. That is the honest reason browser mode can be free without a monthly cap. Cloud HD, when it launches, runs on servers and costs us real money, which is why it uses credits.
When WebGPU is missing
Some older browsers and many older phones do not support WebGPU yet, and running the model without it uses more memory than a browser tab is allowed. On those devices CRD switches to a fast fallback engine that also runs on your device. It is quick and private, but edges are less precise, especially on hair.
For the best result, use a recent version of Chrome, Edge or Safari on a computer. The help article on devices and browsers has the details.
What we are still improving
- Edge quality on difficult photos, such as hair against a busy background.
- Speed on mid range laptops and phones.
- A cloud HD option for the hardest images, for people who want it.
You can follow all of this on the roadmap and the changelog.