ComfyUI failed to connect to server
Determine whether the browser, local server or external provider is failing.
Recognize the message
Failed to connect to server; connection refused; request timeout
A connection failure means a request did not complete as expected. A local ComfyUI server connection and an external API node request need different investigation.
Work through the evidence
- Note the destination shown by the browser, timestamp, startup log and whether the ComfyUI process is still running. Remove tokens and private hostnames before sharing evidence.
- Open the address reported by your own running ComfyUI. Check that the configured host and port match, and distinguish an unavailable process from an execution queue issue.
- For an external API node, read its provider status and the node’s error report. Check the documented account setup without pasting secrets into diagnostic tools.
Verify the result
The relevant destination responds and the smallest corresponding action completes. Reconnect the browser and confirm new log timestamps rather than relying on an old failure.
What this does not prove
Do not expose your local server to the internet or disable security protections to make an unexplained connection work. A queued long-running job is not necessarily a network failure.
Inspect before changing your workflow
The log inspector works in your browser. The workflow checker reads exported graph structure. Neither sends files automatically or executes nodes. Preserve the original, inspect a copy and record the actual test result in Casebook.
Inspect your log ↗ · Check the graph ↗ · Record a recovery case ↗Before asking for help
Include the first full exception, the failing stage, software versions, model family and the smallest reproducible graph. Redact API keys, user paths and private prompts. A summary such as “KSampler broken” removes the context that distinguishes one failure from another.
Prepare a redacted copy ↗Related investigations
ComfyUI CUDA out of memory · ComfyUI missing custom nodes · ComfyUI model not found · ComfyUI custom node import failed
Source and scope
These are OnBeg’s diagnostic checklists, informed by official ComfyUI troubleshooting. They are not universal fixes and do not replace model- or extension-specific instructions.