ComfyUI

Node-graph image-generation UI. Standard for Stable Diffusion and Flux workflows. Endlessly customizable.

Download the installer from comfyui.org — available as a standalone desktop app (Windows, macOS, Linux) or via git: git clone https://github.com/comfyanonymous/ComfyUI && cd ComfyUI && pip install -r requirements.txt. Requires Python 3.10+ and CUDA 12.1+ for NVIDIA GPU acceleration (CPU-only fallback available but slow). Launch: python main.py (opens web UI at http://localhost:8188). The Windows desktop app auto-installs dependencies and launches the browser UI. ComfyUI is a node-based visual interface for Stable Diffusion and multi-modal generative models — you build image/video generation pipelines by connecting nodes (load model → prompt encode → sample → decode → save). Download models to models/checkpoints/ (SDXL, SD3, Flux, etc.), VAE to models/vae/, LoRAs to models/loras/. Restart ComfyUI after adding models. First run with the default workflow (load from workflows/ or use the example in the UI) generates a test image in ~30 seconds on a modern GPU. Verify: load the default SDXL workflow → click "Queue Prompt" → image appears in output panel. Time-to-first-image: ~5 minutes including model download (SDXL base is ~7 GB).

Best for: professional image/video generation with fine-grained pipeline control, reproducible workflows where the node graph acts as documentation and version control, batch processing and automated generation via ComfyUI's API, complex multi-pass generation (img2img → upscale → inpaint → refine), production Stable Diffusion pipelines, team environments where sharing workflow JSON standardizes output quality. Not suited for: quick single-image generation from a text prompt (use Automatic1111 or Diffusers), users new to generative AI who benefit from simplified interfaces, mobile/low-resource environments (ComfyUI is desktop GPU-focused), non-technical creative users (node graph is programmer-friendly but artist-hostile without training).

Use ComfyUI when you want maximum control over your image generation pipeline — the node graph editor lets you fine-tune every step (CLIP skip, sampler, scheduler, CFG, denoise strength, control nets, IP-adapter) and build complex multi-pass workflows. It's the professional/production tool for Stable Diffusion. Switch to Automatic1111 when you want a more traditional UI with sliders and forms — WebUI's linear workflow is simpler for basic txt2img and img2img. Use Diffusers when you need programmatic Python control rather than visual node editing. Use InvokeAI for a polished canvas-based generation experience. ComfyUI's strength: workflow reproducibility — save and share entire node graphs as JSON, perfect for team pipelines and automation via its API. Its weakness: steeper learning curve than form-based UIs, overwhelming node library for new users, and a UI that rewards learning the node ecosystem.

Problem: Model fails to load with "KeyError: 'model.diffusion_model...'" Fix: Mismatched model and ComfyUI version. SDXL models need SDXL-specific loaders (use "Load Checkpoint" not "Load Lora" as primary node). SD3/Flux models need their own loader nodes. Ensure the model file is in models/checkpoints/ not a subfolder. After adding models, restart ComfyUI — it scans the models directory at startup. Problem: Queue stuck on "Queue Prompt" with no errors. Fix: ComfyUI's execution queue is sequential — a previous job may be hung. Check the terminal where python main.py is running for errors. Click "Cancel" on the queue panel. Common silent failures: custom node version mismatch (update custom nodes via ComfyUI Manager → "Update All"), insufficient VRAM (check nvidia-smi — if VRAM is at 100%, reduce image resolution or use a smaller model). Problem: Custom nodes fail to install or break after ComfyUI update. Fix: ComfyUI Manager (install via git clone into custom_nodes/) handles node installation. After a ComfyUI update, run "Update All" in Manager. Incompatible nodes are marked in red — disable them until updated. Check the ComfyUI console for import errors on startup.