What are Command Line Arguments?

Command line arguments are extra settings and options you pass when running a program (here, ComfyUI's main.py).

You use them to control lower-level things that the regular settings screen doesn't cover, such as how VRAM is used or network connections.

How to Set

Add the arguments after python main.py when you launch it.

python main.py --fast

In the portable version, right-click the .bat file you use to launch it (e.g. run_nvidia_gpu.bat), choose edit, and add the arguments after python.exe.

List of Arguments

VRAM / Memory Control (Stability and Performance)

For dealing with out-of-VRAM errors (OOM) and tuning behavior to how much VRAM you have.

Argument Name Function Remarks
🔥 --reserve-vram [GB] Reserve VRAM: Sets an amount of VRAM in GB and keeps that much free for the OS and other apps. With --reserve-vram 1.0, at least 1.0GB is left free.
--vram-headroom [GB] Keep additional VRAM free for DynamicVRAM. With --vram-headroom 1.0, ComfyUI tries to leave an extra 1.0GB free.
🔥 --disable-smart-memory Turns off smart memory management. Models aren't kept in VRAM and are aggressively offloaded to RAM. Useful on low-VRAM systems when you want stability first. It may be slower.
--lowvram Enable VRAM saving mode. Runs the UNET in parts to reduce VRAM usage. The standard setting when VRAM is low.
--highvram Keep the model in GPU memory without unloading it to CPU memory. Speeds up model switching on systems with lots of VRAM.
--high-ram Remove RAM usage limits and make it easier to keep models in memory. For systems with plenty of RAM. Memory usage will increase.
--fast-disk Prefer fast disk storage for DynamicVRAM loading and offloading. Useful when using a fast NVMe SSD.
--cpu Use CPU for all processing. Very slow, so it's a last resort when you have no GPU.
--normalvram Force normal VRAM usage even if lowvram is automatically enabled.

Startup / Connection Settings (Convenience and Network)

For browser behavior and sharing ComfyUI over your LAN.

Argument Name Function Remarks
🔥 --disable-auto-launch Disable browser auto-launch. With official Windows Portable, add this to the end of the .bat file if you do not want the browser to open at startup.
🔥 --output-directory [path] Set output directory. For when you want generated images saved somewhere else.
--listen Allow external connections: sets the IP address to listen on. With no value (--listen), it listens on both IPv4 0.0.0.0 and IPv6 ::, so other PCs can connect.
--port [num] Set listen port (default: 8188). Change it when the port is already in use, for example.
--enable-manager Enable ComfyUI Manager. Used to show Manager in the portable and manual installation versions.
--enable-manager-legacy-ui Enable the old ComfyUI Manager UI. Use together with --enable-manager. See ComfyUI Manager for details.
--models-directory [path] Change the location of the models directory. Specify an existing readable directory.
--extra-model-paths-config [path] Load one or more extra_model_paths.yaml files. For when you keep models in more than one place.
--auto-launch Automatically launch ComfyUI in the default browser.

Troubleshooting (Error Isolation / Debugging)

For when ComfyUI won't start, or when something goes wrong, like images coming out black.

Argument Name Function Remarks
🔥 --disable-all-custom-nodes Disable loading of all custom nodes. The most useful way to check whether a custom node is the cause when ComfyUI won't start.
--force-fp32 Force FP32 (single precision). For troubleshooting precision issues, such as black images.
--disable-xformers Disable xformers (acceleration library). Helps tell whether xformers is behind errors or black images.
--fp16-vae Run VAE in FP16 (half precision). Saves VRAM during VAE execution, but black images may be generated.
--cpu-vae Run VAE on CPU. A last resort that hands VAE work to the CPU when VRAM is extremely low.
--disable-metadata Do not save prompt metadata in files. For when you want smaller image files.
--fast Enable untested optimizations. For speed testing. Quality is not guaranteed.

Others (Advanced / For Developers)

Mostly advanced VRAM/precision tuning and frontend testing.

Argument Name Function Remarks
--cuda-device [ID] Set the CUDA device ID used by this instance. For multi-GPU environments.
🔥 --front-end-version [version] For trying out a new UI (frontend). Example: --front-end-version Comfy-Org/ComfyUI_frontend@latest
--temp-directory [path] Set ComfyUI's temporary directory.
--multi-user Enable per-user storage.
--verbose Print more debug output. For detailed error tracking.
--force-channels-last Force channels-last format during model inference.