Updated June 2026
Encountering ‘ComfyUI out of memory’ errors is a common frustration, often manifesting as RuntimeError: CUDA out of memory . This guide provides direct steps to resolve these issues and get your workflow running.
⚡ Quick fix
- Start with understanding “out of memory” errors.
- Start with why this happens.
- Start with initial checks.
- Start with optimize comfyui settings for less vram.
Understanding “Out of Memory” Errors
Encountering ‘ComfyUI out of memory’ errors is a common frustration, often manifesting as RuntimeError: CUDA out of memory. This guide provides direct steps to resolve these issues and get your workflow running.
Why This Happens
ComfyUI, especially with complex workflows or large models, demands significant GPU VRAM (Video RAM). When your GPU runs out of dedicated memory, it triggers this error. Common culprits include high resolutions, large batch sizes, multiple active models, or insufficient VRAM on your graphics card.
Initial Checks
- Close background applications: Ensure no other GPU-intensive programs (games, video editors, other AI tools) are running.
- Monitor VRAM usage: Use tools like
nvidia-smi(for NVIDIA GPUs) or your system’s task manager to monitor VRAM before and during ComfyUI operation. This helps identify if another process is hogging VRAM.
Optimize ComfyUI Settings for Less VRAM
Adjusting your ComfyUI workflow settings is often the most effective way to reduce VRAM consumption.
Reduce Image Resolution
High resolutions consume exponential VRAM.
- In your ComfyUI workflow, locate
Empty Latent Imageor similar nodes that define image dimensions. - Decrease
widthandheightvalues. Start with standard Stable Diffusion resolutions like512x512or768x768and gradually increase if stable.
Decrease Batch Size
If generating multiple images simultaneously, each image adds to VRAM use.
- Find nodes like
Ksampleror any batching nodes. - Set
batch_sizeto1. Generate images one by one instead of in a batch.
Diagnostic checklist before you escalate
Most web-app failures can be narrowed to service status, one account session, browser data, an extension, or the network. Test those boundaries in order rather than clearing everything at once. A private window and a second network are especially useful because they change one layer without altering your account data.
- Check the provider’s official status page before changing local settings.
- Hard-refresh, start a new session, and test a private browser window.
- Disable content blockers, privacy extensions, VPN, proxy, and secure DNS temporarily.
- Compare another browser, device, and network to locate the failing boundary.
- Record timestamps, error text, and the smallest reproducible sequence for support.
| Test | What the result tells you | Next move |
|---|---|---|
| Official status page reports an incident | The service is affected beyond your device | Pause local resets and monitor recovery |
| Private window works | Normal browser data or an extension is involved | Clear site data and enable extensions one by one |
| Another network works | DNS, VPN, proxy, firewall, or filtering is involved | Review the original network configuration |
| Failure follows the account everywhere | Account, plan, quota, or service-side state is likely | Collect evidence and contact official support |
Verify the recovery across session and network boundaries
When ComfyUI Out of Memory starts working, repeat the original action in a fresh tab and then in the normal browser profile. Confirm that buttons, uploads, saved history, and live updates behave normally instead of only rendering the first screen. If private mode works but the regular profile fails, continue isolating cookies and extensions rather than declaring the service fixed.
Restore extensions, VPN, proxy, secure DNS, and content filtering one at a time. Reload after each change. This controlled restoration identifies the incompatible layer and prevents the common outcome where everything is disabled permanently. Finish by testing one other device or network so you know whether the recovery belongs to the account, the device, or the connection.
- The original action succeeds twice in a fresh session.
- The normal browser profile works after cleanup.
- Extensions and network controls are restored individually.
- Saved data and account history remain available.
- A second device or network confirms the result.
Keep a short note of the working configuration and the date of the test. Products, models, browser versions, limits, and safety policies change over time, so a previously successful workaround may later become obsolete. Prefer current official documentation over old forum instructions, and reverse temporary diagnostic changes once testing is complete. This gives you a reliable baseline without leaving extensions disabled, security controls weakened, or experimental settings enabled indefinitely. Recheck the baseline after major updates before assuming an older failure has returned for the same reason.
When none of the fixes work
Repeat the smallest failing action once and record the exact local time and time zone. Note the product, model or feature, account plan, browser or app version, operating system, and whether the same action works in a private window, on another device, or on another network. This evidence is much more useful than saying the tool is “still broken.”
Use the provider’s official support channel. Include a screenshot with sensitive information removed and list the steps already tested. For developer tools, add sanitized request and response details, correlation IDs, and SDK versions. Never send passwords, one-time codes, API keys, session cookies, private repository contents, or complete payment information.
FAQ
- Q: Can I use multiple GPUs to solve VRAM issues?
- A: ComfyUI doesn’t natively combine VRAM from multiple GPUs for a single workflow. It primarily utilizes one GPU unless specific custom nodes are designed for multi-GPU distribution (rare).
- Q: Does system RAM (CPU RAM) affect ComfyUI’s performance?
- A: Yes, especially when offloading data from VRAM using
--lowvramor--medvramarguments. Sufficient system RAM prevents bottlenecks there. - Q: My ComfyUI workflow used to work, but now I get VRAM errors. Why?
- A: This often happens after loading a new, larger model, increasing resolution, adding more complex custom nodes, or after a system update that changed resource allocation. Revisit your recent changes.
By optimizing ComfyUI settings, managing system resources, and using appropriate launch arguments, you can effectively resolve “ComfyUI out of memory” errors.
Bottom line: Work from the least disruptive test to the most specific one. Confirm service health, isolate session and network variables, then escalate with clean evidence instead of repeating the same failing action.
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