Closed model
A model you can only reach through someone’s API — the weights stay locked behind the vendor’s door.
Think of it like
A restaurant kitchen you order from but never enter; you get the dish, never the recipe.
Example
Using a top proprietary model means sending prompts to its API and getting answers back — you never hold the weights.
How it actually works
Closed models keep parameters private and are served via API. You trade control and data locality for convenience, managed scaling, and often frontier quality. The risks are lock-in, price changes, and sending your data to a third party.
For product teams
Fastest path to frontier quality, but watch for lock-in, data exposure, and pricing you don’t control.
For engineers
API-gated model with undisclosed weights; you consume inference without hosting or inspecting it.
Related
- Open weights — The opposite is open weights.
- Frontier model — Often a frontier model.
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