The SD WebUI that started it all — still powerful, still free, still updated.
Automatic1111 (a.k.a. A1111, SD WebUI) is the Python/Gradio app that defined what local Stable Diffusion looks like. Born in 2022, it's still actively maintained and has the largest extension ecosystem in the SD world. If you want to run SD 1.5, SDXL, or any community model locally, A1111 is the most-documented, most-tweaked, most-extensible path. ComfyUI is newer and faster, but A1111 is friendlier for one-off generation and has way more tutorials online.
Who it's for: AI artists with GPUs who want full local control. Anyone who learned SD before ComfyUI existed and doesn't want to switch. Researchers who need the most extensible base. Not for users without a GPU or who want plug-and-play — use Midjourney or Leonardo instead.
MIT-style license, runs on your GPU, no cloud, no per-image cost. The de-facto open-source SD UI. Install on Windows, Mac, or Linux with one bash script.
1000+ community extensions: ControlNet, LoRA, ADetailer, Inpaint, Outpaint, Dynamic Prompts, LyCORIS, regional prompting, super-resolution. All installable from the Extensions tab.
Drop any SD 1.5, SDXL, or community fine-tune checkpoint into the models folder. Safetensors, pickles, diffusers — all supported. Hot-swap models without restarting.
Run with --api flag and you get a REST API. Pipe to ComfyUI, custom frontends, or your own product. The de-facto backend for many SD-as-a-service products.
Automatic1111 is the SD WebUI you start with, and many people stay with it forever. The form-based UI is more intuitive than ComfyUI's node graphs, and the extension ecosystem is unmatched. For pure speed and reproducibility, ComfyUI wins. For one-off art, learning, and the most online help available, A1111 is still king. Both are free — install both and use whichever fits the task.