A language model sits in front of the generator and fills in what you left out — lens, light, texture, mood. Six words become sixty. For a casual prompt this is usually an upgrade, because the generator behaves better with specifics and most people write far too little.
The cost is that you are no longer the author of the input. Two runs of the same short prompt can be expanded differently, so results vary in ways the seed cannot explain, and a detail you deliberately omitted may be invented and inserted. If you have written a careful, precise prompt, expansion can overwrite exactly the restraint you were going for.
It appears under several names across providers and is frequently on by default. Whether it is on is worth knowing before you spend an afternoon concluding that a model ignores your wording.
In practice
- On by default for many models — check before assuming your text reached the generator verbatim.
- Turn it off when reproducing a result exactly, because the rewrite is a second source of randomness.
- Leave it on for quick exploration from short prompts; it raises the floor considerably.
The mistake to avoid
Debugging a locked seed while expansion is enabled. The seed is doing its job; the prompt going in was different each time.
Where you will run into it
- Text to Image Generator — One prompt. Catalog image models. One studio.
- AI Video Generator — Text-to-video, image-to-video, and story chaining in one studio.
- AI Movie Maker — One prompt. A finished short film.
Related terms
Prompt
Prompt meaning: the written instruction a generative model reads to decide what to make. The one input almost every model needs.
Prompt adherence
Prompt adherence meaning: how faithfully a model does what the prompt said, not just something attractive nearby.
Seed
Seed meaning: the number that sets the random starting noise so the same seed and settings can reproduce the same output.
Negative prompt
Negative prompt meaning: a list of what you do not want in the output, steering generation away from those terms.
Aspect ratio
Aspect ratio meaning: width-to-height proportion of an output, written as two numbers (16:9 landscape, 9:16 full phone).
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