If you want to generate images on your own computer with open models such as Stable Diffusion XL or Flux, two free interfaces dominate: ComfyUI and Stable Diffusion WebUI Forge. Both are open source and both run on your own GPU, but they suit very different working styles.
The one-line difference
- Forge is a classic web app with tabs, prompt boxes and sliders. You type a prompt, adjust settings and press Generate.
- ComfyUI is a node graph. You connect boxes (model, prompt, sampler, upscaler) with wires to build a pipeline, then run it.
WebUI Forge: familiar and light on memory
Forge was created by lllyasviel, the developer behind ControlNet, as a faster and more memory-efficient version of the well-known AUTOMATIC1111 Stable Diffusion WebUI. If you have used AUTOMATIC1111, Forge looks almost the same, and many of its extensions work.
Strengths
- Easy to learn: prompt, negative prompt, steps, size, Generate.
- Good memory management, which helps on graphics cards with limited VRAM.
- Runs Flux models in compressed formats (NF4 and GGUF), including with LoRAs.
Things to know
- Development has moved in bursts, and community forks have appeared to keep supporting newer models. Check which version or fork is current before installing.
- Complex multi-step pipelines are harder to build and repeat than in a node graph.
ComfyUI: flexible and repeatable
ComfyUI treats every step as a node. That looks intimidating at first, but it means a whole pipeline, including image-to-image passes, ControlNet, upscaling and video, lives in one graph you can save and share. ComfyUI also embeds the workflow in the images it saves, so dragging an image back in restores the exact setup.
Strengths
- New open models are usually supported quickly, often on release day.
- Handles image, video and audio models, not just still images.
- A large ecosystem of custom nodes, installable through the ComfyUI Manager.
- Workflows are easy to share and reuse exactly.
Things to know
- The learning curve is real. Start from a shared workflow rather than an empty canvas.
- Custom nodes come from many authors; install only what you need and keep them updated.
- Licence is GPL-3.0. There is also Comfy Cloud, a paid hosted service, if you do not have a suitable GPU.
Hardware
Both work best with an NVIDIA graphics card. As a rough guide, 8 GB of VRAM handles SDXL comfortably, while full-size Flux models want 12 GB or more unless you use the compressed versions. Apple Silicon Macs can run both, more slowly than a strong NVIDIA card. If you have no suitable GPU, a hosted option such as Comfy Cloud or a web tool like Leonardo.ai is more practical.
Which should you choose?
Choose Forge if you want to type prompts and get images with the least setup, you are coming from AUTOMATIC1111, or your GPU is short on memory.
Choose ComfyUI if you want to try the newest models as they come out, build repeatable multi-step pipelines, or work with video as well as images.
Many people start with Forge to learn how prompts, samplers and steps behave, then move to ComfyUI when they want more control. Both are free, so installing both and comparing them on your own hardware costs nothing but disk space.
Related: ComfyUI · WebUI Forge · Magnific AI · best AI image generators