Ollama operates as a local background daemon that manages model lifecycle, quantization, and memory allocation. Users download models via the command line using simple pull commands (such as ollama run llama3.3 or ollama run deepseek-r1), which automatically retrieve quantized GGUF weights from the Ollama library. The runtime detects available system hardware—including Apple Silicon Metal, Nvidia CUDA, and AMD ROCm—and offloads model layers to GPU memory dynamically.
Once running, Ollama exposes an HTTP server at http://localhost:11434 with endpoints for generation (/api/generate), chat completions (/api/chat), and OpenAI compatibility (/v1/chat/completions). Developers can customize system instructions, temperature, and context length by authoring custom Modelfiles and building tailored local variants.