If you have ever been building an AI workflow in ComfyUI when a node suddenly turns red and clicking on it brings up a long string of English error messages — this article is for you.
I. Why Red Errors Appear
ComfyUI's node system runs on Python scripts. When a node's input parameters do not meet requirements or a dependency library is missing, the node displays a red background and stops executing. This typically occurs in the following scenarios:
Scenario 1: Incorrect model weight file path (most common)
When you download someone else's workflow JSON file and import it into your own ComfyUI, if the model files used by that person do not exist locally or are stored in a different path, the Load Checkpoint node will show a red error. The solution is to check the specific error message in the queue panel on the right — it will usually clearly tell you which filename is missing. Go to HuggingFace or Civitai to download the corresponding .safetensors file and place it in the models/checkpoints directory.
Scenario 2: Custom node plugins not installed
Someone else's workflow uses third-party plugins like ComfyUI-Impact-Pack or ComfyUI-Manager, but you do not have them installed locally. In this case, the error message will contain the text "ModuleNotFoundError". Solution: Open ComfyUI Manager (click the Manager button in the top toolbar) → search for the missing node name → click Install.
Scenario 3: Input type mismatch
For example, a node requires an IMAGE-type input, but you have connected LATENT-type data. ComfyUI does not automatically convert data types, so it will throw an error. The solution is to add a type conversion node between the two nodes — to convert from LATENT to IMAGE, use a VAE Decode node; conversely, use a VAE Encode node.
II. High-Frequency Error Checklist and Fixes
"No module named 'xxx'"
Missing Python dependency library. Open a command line in the ComfyUI root directory and run pip install xxx to install the missing package. If you are unsure of the exact name, first copy the full module name from the error message.
"CUDA out of memory"
Insufficient GPU memory. Solutions: lower the resolution (e.g., change from 1024x1024 to 512x512); add the --lowvram flag to the ComfyUI startup parameters; or close other programs that are using the GPU.
"Checkpoint file not found"
Model file is missing or the path is configured incorrectly. Check whether the file name mentioned in the error exists in the models/checkpoints directory — note that the case must match exactly.
"Invalid image size: must be multiple of 64"
The resolution is not a multiple of 64. Adjust the width and height to standard sizes such as 800x1200 or 512x768.
III. Best Practices for Preventing Errors
Before importing someone else's workflow, first back up your current project (File → Save Workflow); second, always restart the ComfyUI service after installing new node plugins; third, regularly update the ComfyUI core program and all custom nodes to their latest versions — many errors are caused by outdated plugins being incompatible with a newer core program.
