{"id":3504,"date":"2025-11-19T00:00:00","date_gmt":"2025-11-19T00:00:00","guid":{"rendered":"https:\/\/godofprompt.io\/blog\/2025\/11\/19\/gpt-5-1-vs-gpt-5\/"},"modified":"2025-11-19T00:00:00","modified_gmt":"2025-11-19T00:00:00","slug":"gpt-5-1-vs-gpt-5","status":"publish","type":"post","link":"https:\/\/godofprompt.ai\/blog\/gpt-5-1-vs-gpt-5\/","title":{"rendered":"GPT 5.1 vs GPT 5: What Actually Changed (2026 Comparison)"},"content":{"rendered":"

OpenAI just fixed GPT 5’s biggest problems.<\/p>\n

GPT 5 launched with complaints about feeling robotic and less helpful than older models, leading OpenAI to walk back some decisions and blame performance issues on the model’s router. GPT 5.1 is their response.<\/p>\n

I tested both models for a week. <\/p>\n

Here’s every meaningful difference.<\/p>\n

ALSO READ:<\/strong> How To Use GPT 5.1: Complete Prompting Guide for Developers<\/a><\/p>\n

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Get hundreds of leads on autopilot with PhantomBuster<\/a><\/figcaption><\/figure>\n

Speed: Faster When It Matters, Slower When It Counts<\/h2>\n

GPT 5.1 Thinking varies its thinking time dynamically\u2014roughly twice as fast on simple tasks and twice as slow on complex ones.<\/p>\n

What that actually means:<\/strong><\/p>\n

Simple coding question like “show me an npm command to list global packages”? GPT 5.1 answers in 2 seconds instead of 10.<\/p>\n

Complex algorithm design? GPT 5.1 Thinking takes longer because it’s actually thinking through edge cases instead of guessing fast.<\/p>\n

Real test I ran:<\/strong><\/p>\n

I asked both models to write a function removing duplicates but keeping the last occurrence.<\/p>\n

GPT 5 returned code in 3 seconds. It broke on edge cases with empty lists.<\/p>\n

GPT 5.1 took 3.2 seconds. The code worked on every edge case I threw at it.<\/p>\n

That tiny 200-millisecond hesitation? Worth it. GPT 5.1 finally understands that speed without accuracy is just fancy typing.<\/p>\n

Instruction Following: It Actually Listens Now<\/h3>\n

GPT 5 had a bad habit. You’d say “give me exactly four sentences” and it would give you six.<\/p>\n

When tested with arbitrary rules\u2014write exactly four sentences about The Lion King, none starting with ‘Simba’ or ‘The’\u2014GPT 5 missed the rule about ‘The’ while GPT 5.1 followed every constraint.<\/p>\n

I tested this myself:<\/strong><\/p>\n

Prompt: “Describe the best travel destinations in exactly six words.”<\/p>\n

GPT 5 response:<\/strong> “Beautiful scenery, rich culture, amazing cuisine, friendly locals, great weather, affordable prices.” (10 words)<\/p>\n

GPT 5.1 response:<\/strong> “Scenery culture cuisine climate friendly locals.” (6 words exactly)<\/p>\n

This matters for:<\/p>\n