Fix ComfyUI "Failed to Fetch Server Logs" (VPN & Proxy)
Fix ComfyUI "failed to fetch server logs" by checking the backend terminal, 127.0.0.1, VPN, proxy, firewall, browser requests, and custom nodes.
The browser message failed to fetch server logs (also failed to fetch) means the interface tried to read logs from the server and that request failed. It is usually a second symptom: the backend crashed, or a VPN, proxy, firewall, browser extension, or LAN route blocked the request path. Start outside the browser and look for the real backend error before reinstalling.
If Manager says failed to get custom node list, use ComfyUI Failed to Get Custom Node List. If the main symptom is Reconnecting..., use ComfyUI Reconnecting Error.
If your UI only says Failed to fetch and you are not sure which request failed, start with ComfyUI "Failed to Fetch" and choose the matching branch first.
Triage
| Symptom | Likely meaning | First move |
|---|---|---|
| "failed to fetch server logs" and ComfyUI is offline | The server probably crashed | Check the terminal or portable launch window |
| ComfyUI still works but logs cannot load | Browser/API request failure | Check DevTools Console and Network |
| Started after installing custom nodes | Custom node or frontend extension conflict | Start with custom nodes disabled |
| Happens only over LAN, proxy, VPN, or remote access | Network, bind address, firewall, or auth issue | Test from http://127.0.0.1:8188 |
failed to fetch versions from ComfyRegistry or Manager list fails | Manager/registry network problem | ComfyUI Failed to Get Custom Node List |
| Terminal shows a real traceback | The traceback is the real issue | Fix the first terminal error |
Step 1: Do not treat the browser message as the root cause
ComfyUI has a Python server (terminal log) and a browser interface. The browser can fail to fetch logs even when the true problem is elsewhere. Find the original Python-side error first.
- Portable: the console window opened by
run_nvidia_gpu.batorrun_cpu.bat. - Manual: the terminal where you ran
python main.py. - ComfyUI Desktop (Windows): logs under
C:\Users\<username>\AppData\Roaming\ComfyUI\logs.
Step 2: Confirm the server is running
Open http://127.0.0.1:8188. If it does not load, the log message is secondary — the server is offline, crashed, or on a different port. On Windows, check the port:
netstat -ano | findstr :8188If nothing is listening, restart ComfyUI and watch the terminal from the start.
Step 3: Check the browser request path
If the page is still open, press F12 and check:
- Console for JavaScript or websocket errors
- Network for failed requests
- whether requests go to
127.0.0.1,localhost, a LAN IP, or a proxy domain
Then test http://127.0.0.1:8188. If local access works but LAN or proxy access fails, the issue is network-related, not a broken install.
Step 4: Check firewall, antivirus, VPN, or proxy tools
Local security tools, proxies, remote tunnels, and browser extensions can block requests between the browser and ComfyUI even when Python is running. Try:
- temporarily disable VPN or proxy tools
- test in a clean browser profile
- disable aggressive browser extensions
- allow Python or ComfyUI through Windows Firewall
- test from the same machine before another device
Step 5: Start without custom nodes
A broken frontend extension can make parts of the UI fail. For a manual install:
python main.py --disable-all-custom-nodesFor the Windows portable package, copy your launch .bat and add --disable-all-custom-nodes. If the message disappears, binary-search: re-enable half the nodes, restart, and repeat until you find the bad node. For the full path, use ComfyUI Plugin Import Failed.
Step 6: Update the frontend and requirements together
If the error appears after an update, avoid a half-updated stack. After git pull:
Do not run pip install -r requirements.txt blindly.
- Confirm which Python environment is active (
where pythonorwhich python) - Inspect
requirements.txt— check if it pins torch, numpy, or opencv versions - Install only the missing package when possible:
pip install <package-name> - Run
pip checkafter installation to verify no conflicts were introduced
For portable ComfyUI, run pip through the embedded Python from the portable folder. For broader update problems, see ComfyUI Dependency Conflicts.
Step 7: Capture the real log before changing things
Before reinstalling, save the full terminal output, browser Console errors, browser Network failure details, ComfyUI version, Python/PyTorch versions, custom node list, and the workflow that triggered the issue. If the log never reaches Starting server, solve the startup error first — the browser cannot fetch logs from a server that did not finish starting.
Best next step by trigger
| Trigger | Best next guide |
|---|---|
| The page also keeps reconnecting | ComfyUI Reconnecting Error |
| Manager broke around the same time | ComfyUI Failed to Get Custom Node List |
Startup never reaches Starting server | ComfyUI Startup Failed |
| The error started after plugin changes | ComfyUI Plugin Import Failed |
| Updates changed multiple packages at once | ComfyUI Dependency Conflicts |
Related Guides
- ComfyUI Reconnecting Error
- ComfyUI Startup Failed? How to Diagnose and Recover Faster
- ComfyUI Failed to Get Custom Node List
- ComfyUI Dependency Conflicts
Source References
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