text model · gpt-oss · iOS
Can I run gpt-oss 20B on iPhone 17?
No. gpt-oss 20B needs ~13.2 GB even at Q4_K_M, but iPhone 17 only has ~4.5 GB usable.
Needs ~13.2 GB even at Q4_K_M, but only ~4.5 GB is usable.
- Q4_K_M needed
- ~13.2 GB
- Usable on device
- ~4.5 GB
- Device memory
- 8 GB
How to run it
On iOS use Apple Foundation Models (Built into iOS 26, ~3B on-device model, zero download, fully private.). Phones realistically run 1B-4B class models. Anything larger thermally throttles or OOMs.
- Parameters
- 21B (MoE, 3.6B active)
- Q4_K_M size
- 11.28 GB
- Context
- 128k
- Ollama tag
- gpt-oss:20b
- Memory
- 8 GB unified
- Usable for weights
- ~4.5 GB
- Best runtime
- llama.cpp + Metal (via PocketPal or Off Grid app)
What you can run instead
Run gpt-oss 20B on other hardware
FAQ
Can iPhone 17 run gpt-oss 20B?
No. gpt-oss 20B needs ~13.2 GB even at Q4_K_M, but iPhone 17 only has ~4.5 GB usable.
How much memory does gpt-oss 20B need?
iPhone 17 does not have enough memory. At Q4_K_M the weights are ~11.28 GB; with KV cache and runtime overhead, budget ~13.2 GB at a 4k context. It is a Mixture-of-Experts model (21B total / 3.6B active), so all experts must stay in memory; memory tracks total params, not active params.
What is the best tool to run gpt-oss 20B on iOS?
On iPhone and iPad, Apple Foundation Models (Built into iOS 26, ~3B on-device model, zero download, fully private.) is the standard choice. Phones realistically run 1B-4B class models. Anything larger thermally throttles or OOMs.
Sources
Memory figures are estimates. See methodology.