GPT-4.1 nano vs o3 Pro

GPT-4.1 nano

OpenAI

GPT-4.1 nano is OpenAI's smallest member of the GPT-4.1 family, released in April 2025 alongside GPT-4.1 and GPT-4.1 mini as the latency-optimized, cost-minimized option for high-throughput applications. Positioned below GPT-4.1 mini in both size and cost, it was designed for use cases where speed and affordability dominate over raw capability — including tool calling, intent classification, short-form instruction following, and retrieval-augmented lookup tasks. Unlike its larger siblings, it supports fine-tuning, making it a practical candidate for task-specific customization at scale without incurring the cost of fine-tuning larger models.

o3 Pro

OpenAI

OpenAI o3-pro, released by OpenAI in June 2025, is an extended reasoning model from the o3 family that applies more compute per response to deliver deeper, more thorough answers on complex problems. It features a 200K token context window, 100K maximum output tokens, and vision capabilities. o3-pro targets research-grade reasoning tasks, extended coding sessions, and applications where accuracy on difficult problems justifies higher inference cost and latency.