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Glossary · ComfyUI Basics

What Is a Seed in ComfyUI?

By Earngenix Team ·

⚡ Quick Answer

A seed is the starting number ComfyUI uses to generate the initial random noise for your image. The same seed, with every other setting identical, produces the exact same image every time — change the seed and you get a different result even with an unchanged prompt.

Think of it like locking the dice before a roll. A fixed seed means you get a consistent, repeatable outcome while you tweak other things like CFG or a LoRA. A randomized seed means every generation is a fresh roll.

Where You'll See It

The seed field sits inside the KSampler node, next to a control_after_generate dropdown with four options: fixed, increment, decrement, and randomize.

Quick Example

Set the seed to 12345 and control_after_generate to fixed to reproduce the exact same base image every run — useful while you experiment with CFG scale, a new LoRA, or a different sampler and want to compare changes side by side.

If you liked an old result and want it back, you need the same seed and the same checkpoint, prompt, resolution, sampler, and scheduler. Change any one of those and the seed alone won't bring the image back.

Frequently Asked Questions

Any other changed setting — prompt, checkpoint, resolution, sampler, or scheduler — breaks reproducibility even with an identical seed. All of them have to match to get the same result.

The control_after_generate dropdown next to the seed field can automatically change the seed by 1 after each run — useful for browsing small variations without manually retyping a new number each time.

Yes — if your checkpoint, prompt, sampler, scheduler, and resolution all match theirs, you’ll usually get a very similar result. There’s no absolute guarantee across different ComfyUI versions or hardware, but it’s close in practice.

See It In Action

Ready to lock in a reproducible workflow?

Our text-to-image guide shows exactly where seed control fits alongside CFG and sampler settings.

Published: 2026-08-25 · Last updated: 2026-08-25

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