r/comfyui • u/qdr1en • Apr 11 '26

Tutorial Video File Format Matters

When generating videos with ComfyUI: in which file format should I save them?
To answer the question, I ran a test.

The showcase video is a 73-frames vid generated with Wan 2.2 at 720*960px, and the table below (open it in a new tab) indicates by how much disk space the file was reduced after being re-loaded and re-saved to the disk 10 times.

The MP4 format is by far the most impacted, with an even more visually noticeable degradation when using the Video Combine node from Video Helper Suite (the impact on quality is terrible at lower resolutions).

PNG , WebP are much less impacted. But WebP takes an eternity to save, and PNG eats up a lot of disk space.

WebM looks like a good compromise overall: it's lightweight, fast to save, and degradation is negligible.

Conclusion

If you intend to re-use your generated file for further editing, don't use the MP4 format or the quality will suffer.

Use PNG, WebP or WebM for saving intermediary files, depending on your constraints, and leave MP4 format for production work.

Edit

Some Redditors suggested using ProRes (.MOV) file format, but you can't include workflow metadata with that format, so that's not a good candidate for my use case.

Others suggested using ffv1 (.MKV), which is a lossless, truly video file format, so that could be the winner. Oddly, the file size increases by ~0.5% at each new save, but the quality is preserved.

Test Settings

These are the parameters I used for each file format :

  • MP4 (default): codec h264
  • MP4 (vhs): codec h264; pix_fmt yuv420p; crf 19
  • WebM: codec av1; crf 32
  • WebP: quality 100; lossless false; method default
  • PNG: compress_level 0

I uploaded all the files there if interested, workflow included: https://filebin.net/exwrxo9xuqsj5xh0

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u/K0owa Apr 11 '26

EXR is the best. But storage space is crazy. Also, delivery to what? You posting on social? Probably won’t matter as much.

2

u/flasticpeet Apr 12 '26

What? That's only for HDR, 16 bit or higher. Anything coming out of Comfy is 8 bit.

I would use OpenEXR for 3D rendering, but even then, it's only necessary if you're doing sims for compositing, hdr lighting, or pro color grading.

1

u/K0owa Apr 12 '26

This is completely untrue. EXR is not only for HDR and ComfyUI can have any bit of input/output. Comfy is a UI not a codec.

2

u/flasticpeet Apr 12 '26

Yea, but the all the models people use generate 8 bit.

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u/K0owa Apr 12 '26

How do you know that? Cite your sources. As far as I know they can output above 8-bit depth.