GPT-5.1 vs. GPT-5 in ChatGPT: What We Learned Comparing Both Models

GPT-5.1 vs GPT-5 in ChatGPT mainly comes down to how reliably each model follows instructions, how natural the replies feel, and how well it handles images and complex tasks. GPT-5.1 is an OpenAI upgrade that makes ChatGPT more consistent, easier to understand, and better aligned with how real people ask questions and expect answers.¹’²

Key takeaways

• GPT-5.1 is an OpenAI update to the GPT-5 series, not a brand-new generation, but it delivers noticeable gains in tone, reliability, and control.

• GPT-5.1 comes in two main variants, Instant and Thinking, plus automatic routing in ChatGPT that picks the right one for each request.

• In side-by-side tests, GPT-5.1 followed instructions and word limits more reliably than GPT-5 and explained its reasoning in a more approachable way.

• GPT-5.1 handled images better in practical comparisons, keeping faces and outfits more consistent while giving clearer visual explanations.

• For most everyday ChatGPT use, GPT-5.1 is the better default, while GPT-5 remains available as a solid backup for users who want to compare models themselves.

What is GPT-5.1, and how is it different from GPT-5?

GPT-5.1 is OpenAI’s next step in the GPT-5 family.

Instead of replacing GPT-5 outright, GPT-5.1 refines it with better instruction following, clearer explanations, and more control over tone and personality inside ChatGPT.¹

OpenAI describes GPT-5.1 as an upgrade along three main lines:²’⁴

• Adaptive reasoning – the model spends more time on hard questions and less on simple ones.

• Communication style – replies aim to feel more natural and less like a textbook.

• Personalization and safety – users get more control over tone, while OpenAI adds updated safeguards.

In simple terms, GPT-5.1 keeps the same general abilities as GPT-5, but tries to make the experience smoother, clearer, and more dependable.

How does GPT-5.1 work inside ChatGPT?

OpenAI has tied GPT-5.1 deeply into the ChatGPT interface.²

When we open ChatGPT today on a paid plan, we typically see multiple options related to GPT-5.1:

• GPT-5.1 Instant – tuned for speed and everyday chat.

• GPT-5.1 Thinking – tuned for tougher tasks that need more reasoning.

• Automatic routing – ChatGPT can choose between these variants for us behind the scenes.³’⁴

For most people, this means we do not have to pick a model every time.

ChatGPT and OpenAI’s routing decide whether an answer needs quick, light support (Instant) or deeper step-by-step thinking (Thinking).

Where does GPT-5.1 feel better than GPT-5 in everyday use?

1. Instruction following and word limits

OpenAI and independent reviewers agree that GPT-5.1 is better at following detailed instructions than GPT-5.⁴

Examples include:

• Sticking to a specific word count for product descriptions.

• Respecting format requests, like “answer in a table” or “use bullet points only.”³

• Handling multiple constraints at once, such as tone, length, and structure in a single prompt.

In TechRadar’s comparison inside ChatGPT, GPT-5.1 stayed within the requested limits and still sounded more natural, while GPT-5 tended to over-explain and feel more textbook-like.¹

2. Warmth, clarity, and tone

OpenAI calls GPT-5.1 a more conversational model that reflects user feedback about wanting replies that feel human but still precise.²

Testers noticed that GPT-5.1:¹

• Used simpler language when explaining concepts like motion sickness.

• Avoided sounding like a medical textbook unless explicitly asked.

• Managed to be friendly without talking down to the reader.

GPT-5, on the other hand, often answered correctly but packed more jargon and detail into its explanations, which made some replies harder to digest.⁴

3. “Show your work” reasoning

GPT-5.1 Thinking is designed to show its steps more clearly on complex tasks.²⁶

In OpenAI’s evaluations and hands-on tests by writers and developers:⁴

• GPT-5.1 laid out math and logic steps in a more organized way.

• It used fewer undefined technical terms in long explanations.

• It was more willing to walk through a problem gradually rather than jumping straight to a final answer.

OpenAI’s own numbers on coding and reasoning benchmarks (such as SWE-bench Verified and GPQA) also show small but real gains over GPT-5 at higher reasoning settings.⁶

How does GPT-5.1 handle images compared with GPT-5?

TechRadar ran several image-focused tests directly in ChatGPT, comparing GPT-5.1 and GPT-5 on the same prompts.

Two areas stood out:

1. Facial consistency in edits

• When asked to edit a photo of the author but keep his face and outfit the same, GPT-5.1 stayed closer to the original image.

• GPT-5 tended to drift, producing a person who looked more like a stand-in than the same individual.¹

2. Visual reasoning and outfit classification

• Using the same photo, GPT-5 labeled the outfit as “business-casual” but sounded uncertain.

• GPT-5.1 confidently classified it as “dressy,” with a clear explanation based only on what was visible in the image.¹

These tests do not prove that GPT-5.1 wins every possible image task. But they suggest that, in ChatGPT, GPT-5.1 does a better job respecting visual constraints and explaining what it sees.

What does GPT-5.1 mean for work, study, and daily life?

In ChatGPT, GPT-5.1 is mainly about making everyday use less frustrating.

Based on OpenAI’s rollout notes and third-party testing, we can expect:

• For work: more reliable formatting, clearer reasoning, and better support for coding and planning tasks.

• For study: explanations that stay accurate but use fewer technical terms unless we ask for them.

• For daily life: trip plans, summaries, and personal writing that feel more natural and easier to adjust for tone.

OpenAI is also surfacing new tone and style controls so we can tell ChatGPT to sound more professional, direct, casual, or quirky and have those preferences actually stick across chats, something GPT-5 struggled with.⁵

Should we switch from GPT-5 to GPT-5.1 in ChatGPT?

For most people using ChatGPT regularly, the answer is yes.

OpenAI is already rolling GPT-5.1 out to paid ChatGPT tiers and plans to keep GPT-5 available as a legacy option so users can compare them over a transition period.²

In practice:

• If we care about tone, clarity, and instruction following, GPT-5.1 is the better default.⁴

• If we have a workflow already tuned to GPT-5, we can keep it as a backup model and switch as needed.³

GPT-5 remains very capable, but GPT-5.1, as implemented by OpenAI inside ChatGPT, generally feels like the more refined everyday choice.

Frequently Asked Questions

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Citations

1. Schwartz, Eric Hal. “I Compared GPT-5.1 to GPT-5 on ChatGPT, and Now I Don’t Want to Go Back.” TechRadar, 14 Nov. 2025.
2. OpenAI. “GPT-5.1: A Smarter, More Conversational ChatGPT.” OpenAI, 12 Nov. 2025.
3. OpenAI. “Introducing GPT-5.1 for Developers.” OpenAI, 13 Nov. 2025.
4. Waples, Josef. “GPT-5.1: Two Models, Automatic Routing, Adaptive Reasoning, and More.” DataCamp, 13 Nov. 2025.
5. Southern, Matt G. “OpenAI Releases GPT-5.1 With Improved Instruction Following.” Search Engine Journal, 12 Nov. 2025.