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Model

GPT-5.1

GPT-5.1 is an update to GPT-5 released by OpenAI on 12 November 2025. It added a warmer default personality with selectable styles, and its API version has been scheduled for shutdown in 2027.

Status DeprecatedModality Text, ImageContext (K tokens) 400 Era Generative AI for everyone

License
Proprietary
Access
API, App
Release date
Developer
OpenAI

What it is

GPT-5.1 is an update to GPT-5 released by OpenAI on 12 November 2025. It launched as two models, GPT-5.1 Instant and GPT-5.1 Thinking, and the family grew to five models within a week.[1]

Origins

GPT-5.1 is a successor of GPT-5, and it was itself followed by GPT-5.2 in December 2025.[1] Reviewers called it an incremental improvement with better prompt following.[1]

Main features

OpenAI made the default personality warmer than GPT-5's and offered eight selectable personality options.[1][2] The personality setting controls the tone of replies.

Paid Pro, Plus, Go and Business users received early access, and then all users got the model. It was also included in Microsoft Copilot.[1]

On release day the family also included GPT-5.1-Codex-Mini, a lower-cost coding model.[1] GPT-5.1-Codex-Max and GPT-5.1 Pro followed on 19 November 2025. GPT-5.1 Pro replaced GPT-5 Pro in the lineup.[1]

The two launch models reflect a split that runs through the GPT-5 family: an Instant model is built for quick replies, while a Thinking model spends more steps reasoning before it answers. The Thinking variant usually takes longer as a result.

Developer specifications

In the API, GPT-5.1 has a 400,000-token context window and can output up to 128,000 tokens. Its knowledge cutoff is 30 September 2024. Its reasoning effort defaults to none, meaning the model does not reason at length unless a higher level is set.[3]

The API prices were $1.25 per million input tokens and $10 per million output tokens. GPT-5.1-Codex-Mini cost $0.25 for input and $2 for output.[3][5]

A notable behaviour

OpenAI later traced a habit of mentioning goblins and gremlins, first noticed in GPT-5.5, back to GPT-5.1 and to a reward used to train the Nerdy personality.[6] In training, a reward is a score that tells the model which outputs are preferred. A habit that a reward encourages can spread into behaviour beyond the setting it was meant for.

Retirement

Several related API models were shut down on 23 July 2026. These were gpt-5.1-codex, gpt-5.1-codex-mini and gpt-5.1-chat-latest. The gpt-5.1 API model was deprecated on 1 October 2026, with shutdown set for 1 April 2027.[4] Shutdown dates matter for readers who still use an older model, because it stops responding on that date.

CapabilitiesLarge language modelsReasoning

ApplicationsConsumer apps

Version history

22
  1. 2018
    • Jun 11, 2018 GPT-1

      GPT-1 was OpenAI's first generative pre-trained transformer, published in June 2018. It showed that one language model, pre-trained on unlabelled text and then fine-tuned, could improve results on many language tasks.

  2. 2019
    • Feb 14, 2019 GPT-2

      GPT-2 is a large language model that OpenAI announced in February 2019. Its largest version has 1.5 billion parameters. OpenAI first withheld the full model, then released it in stages through November 2019.

  3. 2020
    • May 28, 2020 GPT-3

      GPT-3 is an autoregressive language model with 175 billion parameters, described in a May 2020 paper. It could perform new tasks from a few examples in the prompt, without any gradient updates, and it was first offered through OpenAI's API.

  4. 2022
    • Mar 15, 2022 GPT-3.5 (text-davinci-002/003)

      GPT-3.5 is the family of OpenAI language models between GPT-3 and GPT-4, released through API models such as text-davinci-002 and text-davinci-003 and underlying the first version of ChatGPT.

  5. 2023
    • Mar 1, 2023 GPT-3.5 Turbo

      GPT-3.5 Turbo was the chat-optimised GPT-3.5 model OpenAI released through its API on 1 March 2023, priced at a tenth of the cost of earlier models and later replaced in ChatGPT by GPT-4o mini.

    • Mar 14, 2023 GPT-4

      GPT-4 is OpenAI's large multimodal model, released on 14 March 2023. It accepts image and text input, scored near the top of human test-takers on a simulated bar exam, and was succeeded by GPT-4 Turbo, GPT-4o and GPT-5.

    • Nov 6, 2023 GPT-4 Turbo

      GPT-4 Turbo is a cheaper, more capable version of OpenAI's GPT-4, announced on 6 November 2023 with a 128,000-token context window and lower API prices.

  6. 2024
    • May 13, 2024 GPT-4o

      GPT-4o is a multimodal model from OpenAI, released in May 2024, that takes text, audio, image and video as input and generates text, audio and image output within one neural network. It was removed from ChatGPT in February 2026.

    • Jul 18, 2024 GPT-4o mini

      A small, low-cost language model OpenAI released on 18 July 2024, priced far below GPT-4o and reported at 82% on MMLU; it replaced GPT-3.5 Turbo in ChatGPT on launch day.

    • Sep 12, 2024 OpenAI o1

      OpenAI o1 is the first reasoning model series from OpenAI, introduced in September 2024. It thinks through a long internal chain of thought before answering, and it was the base for later reasoning models such as o3.

  7. 2025
    • Feb 27, 2025 GPT-4.5

      GPT-4.5 is a large language model OpenAI released on 27 February 2025 under the code name "Orion". It was its largest chat model at the time, priced far above GPT-4o, and was retired from general availability within months.

    • Apr 14, 2025 GPT-4.1 (with mini and nano)

      OpenAI's April 2025 family of three API models — GPT-4.1, GPT-4.1 mini and GPT-4.1 nano — offering a context window of over a million tokens, low prices per token and stronger coding scores. It was succeeded by GPT-5.

    • Apr 16, 2025 OpenAI o3

      OpenAI's second-generation reasoning model, announced in December 2024 and released in April 2025, which posted large gains over o1 on science, software-engineering and competitive-programming benchmarks before being succeeded by GPT-5.

    • Aug 7, 2025 GPT-5

      GPT-5 is OpenAI's fifth GPT foundation model, released on 7 August 2025. It pairs a fast model with a deeper reasoning model and a router that chooses between them for each request.

    • Nov 12, 2025 GPT-5.1 · This page

      GPT-5.1 is an update to GPT-5 released by OpenAI on 12 November 2025. It added a warmer default personality with selectable styles, and its API version has been scheduled for shutdown in 2027.

    • Dec 11, 2025 GPT-5.2

      GPT-5.2 is a model family OpenAI released on 11 December 2025, with Instant, Thinking and Pro versions and a coding variant. It was aimed at professional work such as spreadsheets and presentations.

  8. 2026
    • Mar 5, 2026 GPT-5.4

      GPT-5.4 is a model OpenAI released on 5 March 2026 in Thinking and Pro versions. It added built-in computer use and improved deep research, and it was the model that succeeded GPT-5.2.

    • Apr 23, 2026 GPT-5.5

      GPT-5.5 is an OpenAI model released on 23 April 2026 as GPT-5.5 Thinking and Pro, with an API version the next day. It succeeded GPT-5.4 and had a cybersecurity variant in limited preview.

    • Jul 8, 2026 GPT-Live-1

      GPT-Live-1 is OpenAI's full-duplex voice model family, launched 8 July 2026, which lets ChatGPT listen and speak at the same time and replaced the earlier chained speech pipeline in ChatGPT Voice.

    • Jul 9, 2026 GPT-5.6 (Sol, Terra and Luna)

      OpenAI's three-model family released on 9 July 2026 — Luna, Terra and Sol, ordered from least to most capable — with Sol pitched as the company's strongest coding and agent model.

    • Sep 3, 2026 GPT-6 (Astra, Sol, Luna, Instant)

      GPT-6 is OpenAI's sixth-generation model family, launched from 3 September 2026 with GPT-6 Astra, followed by Sol, Luna and Instant. Astra was the first OpenAI model to reach its internal critical cybersecurity threshold.

    • Sep 29, 2026 GPT-6.1 (Sol and Terra)

      OpenAI's late-2026 model family: Sol, released at DevDay on 29 September 2026, and the faster, cheaper Terra on 26 October 2026. A planned Astra version was withheld over safety concerns.

20251

  1. ReleaseOpenAI releases GPT-5.1 with personality presets

    On 12 November 2025 OpenAI released GPT-5.1 Instant and GPT-5.1 Thinking in ChatGPT, giving the chatbot a warmer default tone and eight selectable personality presets.

Developed by1

OpenAI

Foundation for1

GPT-5.1-Codex-Max

Successor of1

GPT-5

Succeeded by1

GPT-5.2

Powers2

Codex (OpenAI coding agent)ChatGPT

Uses1

Chain of thought and reasoning models

Notes and sources

  1. GPT-5.1https://en.wikipedia.org/wiki/GPT-5.1
  2. OpenAI says the brand-new GPT-5.1 is 'warmer' and has more 'personality' optionshttps://www.theverge.com/news/802653/openai-gpt-5-1-upgrade-personality-presets
  3. GPT-5.1 Model | OpenAI APIhttps://developers.openai.com/api/docs/models/gpt-5.1
  4. Deprecationshttps://developers.openai.com/api/docs/deprecations
  5. OpenAI model release dateshttps://opper.ai/model-releases/openai
  6. GPT-5.5https://en.wikipedia.org/wiki/GPT-5.5

Cite this page: GPT-5.1. TellWorld, https://www.tellworld.net/models/gpt-5-1. Updated 2026-11-08