Short answer (2026): For a fast, clean upscale, use the Load Upscale Model + Upscale Image (Using Model) nodes with an ESRGAN model (put models in ComfyUI/models/upscale_models). For maximum quality at high resolutions, use Ultimate SD Upscale (tiled + img2img), keep denoise around 0.3–0.5, and upscale gradually (2× → 4×) rather than jumping straight to 4K.
- Simple/fast: Load Upscale Model → Upscale Image (Using Model)
- Best quality / high-res: Ultimate SD Upscale (tiled)
- Best general model: 4x-UltraSharp (realism: Real-ESRGAN; anime: 4x-AnimeSharp)
- Golden settings: denoise 0.3–0.5, upscale in steps
Method 1 — simple model upscaling (fast)
- Download an upscaler model into
ComfyUI/models/upscale_models. - Add Load Upscale Model (
UpscaleModelLoader) and Upscale Image (Using Model) (ImageUpscaleWithModel). - Feed your generated image in, pick the model, and it enlarges + reconstructs detail in one pass.
This is pure model upscaling — fast, no diffusion. Great for a quick 2×/4× with clean edges.
Method 2 — Ultimate SD Upscale (best quality)
For higher fidelity, diffusion-based upscaling reconstructs texture and fine detail instead of just enlarging pixels. Ultimate SD Upscale does this in tiles, so it works even on limited VRAM:
- Splits the image into tiles, runs img2img on each, and stitches them — avoids the memory wall of upscaling a huge image at once.
- Keep denoise ~0.3–0.5: low enough to preserve structure, high enough to add real detail. Too high and it hallucinates/changes the image.
- Pair it with an ESRGAN model as the base upscaler for best results.
If VRAM is tight, tiled workflows (Ultimate SD Upscale / Tiled Diffusion) are the answer — same principle as running Flux on 8GB.
Best upscaler models
| Model | Best for |
|---|---|
| 4x-UltraSharp | General-purpose, high quality |
| Real-ESRGAN | Realistic photo enhancement |
| 4x-Foolhardy Remacri | Superior texture reconstruction |
| 4x-AnimeSharp | Anime / illustration |
Best practices
- Upscale gradually: 2× then 2× again beats a single 4× jump for small source images.
- Keep denoise low (0.3–0.5) in diffusion upscales to preserve the original.
- Match the model to the content — don't use an anime upscaler on a photo.
Ultimate SD Upscale is a custom node — grab it (and the essentials) via our best ComfyUI custom nodes guide.
Frequently asked questions
How do I upscale an image in ComfyUI?
For a fast upscale, use the Load Upscale Model and Upscale Image (Using Model) nodes with an ESRGAN model placed in ComfyUI/models/upscale_models. For best quality, use Ultimate SD Upscale with denoise around 0.3–0.5.
What is the best upscaler model for ComfyUI?
4x-UltraSharp is the best general-purpose choice. Use Real-ESRGAN for realistic photos and 4x-AnimeSharp for anime/illustration.
What denoise should I use when upscaling?
For diffusion-based upscaling (like Ultimate SD Upscale), keep denoise around 0.3–0.5 — low enough to preserve the original image structure while still reconstructing detail.
Why does my upscale change the image too much?
Your denoise is too high. Lower it to ~0.3–0.4, and upscale gradually (2× → 4×) instead of jumping straight to a large factor.
Conclusion
Two tools cover everything: model upscaling for speed, Ultimate SD Upscale for fidelity. Keep denoise low, go in steps, and match the upscaler to your content. What's your upscaling stack? Share it below.
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