ModuleNotFoundError: No module named 'yaml' in ComfyUI
Fix ComfyUI ModuleNotFoundError: No module named 'yaml' — the actual package name is PyYAML, not yaml.
If ComfyUI logs ModuleNotFoundError: No module named 'yaml', the fix is not pip install yaml. The correct package name is PyYAML.
This is one of the most confusing Python packaging mismatches. The import statement is import yaml, but the pip package is called PyYAML. Installing a package literally named yaml from PyPI will either fail or install the wrong thing.
In the Windows portable SEO Lab repair chain, missing yaml appeared after the database dependencies moved forward. Installing PyYAML exposed the next blocker, which confirmed the active ComfyUI Python was the right repair target.
Fast answer
For the GitHub Windows portable package:
.\python_embeded\python.exe -s -m pip install PyYAML
.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-buildDo not run pip install yaml — that is a different, outdated package.
What the error looks like
IMPORT FAILED: ComfyUI-SomeNode
Traceback (most recent call last):
File "...\custom_nodes\ComfyUI-SomeNode\nodes.py", line 2, in <module>
import yaml
ModuleNotFoundError: No module named 'yaml'You may also see it during ComfyUI startup if a configuration loader or custom node uses YAML for config files.
Why it happens
- The custom node's
requirements.txtlistsPyYAMLbut it was never installed - A previous environment repair or reinstall removed PyYAML as a side effect
- You are running ComfyUI in a minimal Python environment that does not include PyYAML
- ComfyUI's own
requirements.txtmay include PyYAML, but the portable package setup skipped it
The package name trap
| What you type | What happens |
|---|---|
pip install yaml | Installs a wrong or broken package — do not use this |
pip install PyYAML | Installs the correct package that provides import yaml |
pip install pyyaml | Also works — pip package names are case-insensitive |
This is a common Python packaging gotcha. The import name (yaml) does not match the package name (PyYAML).
Safe manual fix
Step 1: Check if PyYAML is already installed
.\python_embeded\python.exe -s -m pip show PyYAMLIf it shows nothing, the package is missing. If it shows a version, the problem may be that a different Python is launching ComfyUI.
Step 2: Install PyYAML
For Windows portable:
.\python_embeded\python.exe -s -m pip install PyYAMLFor a manual venv:
python -m pip install PyYAMLStep 3: Restart and verify
.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-buildThe IMPORT FAILED line should disappear from the startup log.
When not to run pip install blindly
PyYAML is generally safe to install, but watch for:
- Version conflicts if a custom node pins a specific PyYAML version
- The wrong package:
pip install yamlinstalls a completely different, unmaintained package - Installing into a system Python instead of the ComfyUI environment
Always verify you are installing into the same Python that launches ComfyUI.
How Wonderful Launcher can help
Wonderful Launcher can help detect and resolve this issue. It knows the correct package name mapping and helps install PyYAML in the right environment without the naming confusion.
Download Wonderful Launcher — it's free and can recover your environment without reinstalling.
Related errors
- Repair ComfyUI Portable Dependencies One Missing Module At A Time
- No module named 'PIL' in ComfyUI
- ComfyUI Plugin Import Failed
- ComfyUI Dependency Conflicts
- ComfyUI Startup Failed
- Plugin Missing Module Warning: When It Is Safe to Ignore
Source References
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