OpenAI: gpt-5.1-chat-latest:free

gpt-5.1-chat-latest:free
128K context16.4K outReasoningToolsVisionFilesCacheStructuredWeb searchStreamingSystem msg
Released Nov 13, 2025Knowledge cutoff 2024Updated Nov 13, 2025

GPT-5.1 Chat (AKA Instant is the fast, lightweight member of the 5.1 family, optimized for low-latency chat while retaining strong general intelligence. It uses adaptive reasoning to selectively “think” on harder queries, improving accuracy on math, coding, and multi-step tasks without slowing down typical conversations. The model is warmer and more conversational by default, with better instruction following and more stable short-form reasoning. GPT-5.1 Chat is designed for high-throughput, interactive workloads where responsiveness and consistency matter more than deep deliberation.

Mode chatTokenizer GPTReasoning levels none, minimal

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Pricing

Input price
$0.00/ 1M tokens
Output price
$0.00/ 1M tokens
Context window 128K tokensCompatible endpoints openaiVendor OpenAI

Performance

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Usage & Ranking

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Supported parameters

All providers = every upstream serving this model supports it. Some providers = depends on which upstream handles the request. Default = the value sent when you leave the parameter unset.

ParameterProvidersDefault
frequency_penaltySome providersNot sent by default
max_completion_tokensSome providers-
max_tokensSome providers-
response_formatAll providers-
seedAll providers-
structured_outputsAll providers-
temperatureSome providersNot sent by default
tool_choiceAll providers-
toolsAll providers-
top_pSome providersNot sent by default

Frequently asked questions

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