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Device profile · macOS

Best local LLMs for Apple M3 Ultra (256GB)

Apple M3 Ultra (256GB) has ~192 GB usable for model weights and runs 65 of 67 popular models. Best tool: LM Studio.

Usable memory
~192 GB
Models run
65
Too large
2
Top pick
235B
Top pick Q4_K_M
Qwen3 235B A22B Yes

Runs at Q4_K_M using ~136.9 GB of ~192 GB usable.

Runs on Apple M3 Ultra (256GB)

Compatible models 65 total

Too large for this device

DeepSeek R1DeepSeek V3

Best way to run models on macOS

Runtime guide macOS

Beginner: LM Studio, Polished GUI, ships MLX on Apple Silicon, one-click model downloads.

Power user: mlx-lm, Apple's MLX framework, usually the fastest on Apple Silicon for the same quant.

vLLM is NOT a Mac tool, it is a CUDA/Linux serving engine. Unified memory is not a fixed VRAM slice; ~70% is usable for weights.

Full macOS tool guide →

FAQ

What is the best local LLM for Apple M3 Ultra (256GB)?

Qwen3 235B A22B is the strongest model that runs comfortably, using ~136.9 GB at Q4_K_M of the ~192 GB usable on Apple M3 Ultra (256GB).

How much of Apple M3 Ultra (256GB)'s memory can I use for a model?

About 192 GB. Apple Silicon shares one unified memory pool; roughly 66-75% is available to the GPU for model weights, the rest is reserved for macOS.

Which tool should I use on macOS?

LM Studio (Polished GUI, ships MLX on Apple Silicon, one-click model downloads.) or mlx-lm for speed. vLLM is NOT a Mac tool, it is a CUDA/Linux serving engine. Unified memory is not a fixed VRAM slice; ~70% is usable for weights.

Sources

Memory figures are estimates. See methodology.