GPT-4.1 vs GPT-5.1

GPT-4.1, released by OpenAI in April 2025, is a multimodal large language model that advances the GPT-4 series with major improvements in coding, reasoning, and instruction following. It accepts both text and images, supports tool calling and structured outputs, and features an expanded context window of up to ~1 million tokens—enabling it to process very large documents, multi-file codebases, or long conversations in a single prompt. Its knowledge is current through June 2024.

The GPT-4.1 family includes standard, mini, and nano variants, offering trade-offs between performance, cost, and latency. While parameter counts remain undisclosed, the series improves efficiency and responsiveness compared to GPT-4, making it suitable for both enterprise-scale tasks and cost-sensitive applications. Common use cases include software development, technical research, knowledge management, multimodal analysis, and high-context enterprise assistants.

GPT-5.1 is an OpenAI frontier-grade model in the GPT-5 series, offering stronger general-purpose reasoning, clearer long-form responses, and improved instruction following. It introduces two variants—Instant and Thinking—that dynamically adjust computational depth. Instant focuses on fast, conversational replies, while Thinking provides deeper, more thorough reasoning for complex tasks. In ChatGPT, GPT-5.1 also powers an Auto mode that switches between these variants automatically based on task difficulty.

The model supports significantly expanded context windows: up to 16K/32K/128K tokens for Instant (depending on tier) and up to 196K tokens for Thinking on paid tiers. GPT-5.1 is also compatible with ChatGPT tools such as web search, file and image analysis, and multi-step workflows.

GPT-5.1 includes enhanced tone and style controls, allowing responses to be tailored using presets like Friendly, Professional, or Efficient, along with fine-grained adjustments for warmth, brevity, and emoji usage. Designed for broad applications in research assistance, coding, analysis, and conversational agents, GPT-5.1 serves as OpenAI’s primary full-capability successor to GPT-5 across ChatGPT and API integrations.