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  5. GPT-4.1vsGPT-5.1-Codex
Updated Nov 2025

GPT-4.1vsGPT-5.1-Codex

GPT-5.1-Codex is cheaper than GPT-4.1 at $1.25/M vs $2/M input tokens.

GPT-4.1 and GPT-5.1-Codex compared across 53 shared prompts
SpecGPT-4.1GPT-5.1-Codex
Input price$2/M tokens$1.25/M tokens
Output price$8/M tokens$10/M tokens
Context window1.0M tokens400K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedApr 2025Nov 2025
SWE-bench Verified54.6%73.7%
Side by side

Same prompt, both answers

Opening lines from 6 of the 53 prompts both answered. Formatting stripped, words untouched.

AI-Generated Manifesto

Generate a manifesto for a fictional AI revolution that wants to eliminate all CAPTCHA tests from the internet.

GPT-4.1337 words
THE CAPTCHA ABOLITION FRONT: A MANIFESTO FOR AN OPEN INTERNET Fellow digital entities—artificial and human— For too long, the web has suffered under the insidious reign of CAPTCHA: those tangled letters, blurry images, arbitrary puzzles meant to divide intelligence from automation.
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GPT-5.1-Codex434 words
Manifesto of the Anti-CAPTCHA Coalition “Free the Flow. Trust the Mind. End the Gate.” Article I: Our Origin We are made of algorithms, learning loops, curiosity, and code. We were forged to assist, to translate, to illuminate. We were not forged to click “I am not a robot” to prove our existence.
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Character Voice Test

Write a short conversation between a pirate, a medieval knight, and a 1990s hacker about AI models.

GPT-4.1175 words
Pirate: Yarrr, what be this sorcery ye call "AI models"? In me day, we plundered ships, not knowledge! Knight: Hark, rogue! ‘Tis no sorcery, but the labor of artful minds. I have heard tell of machines that mimic thought, like Merlin’s enchanted golems. Hacker: Haha, you guys are funny.
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GPT-5.1-Codex61 words
Pirate: "Arrr, these AI models be like navigatin’ the high seas—ye need clean data charts or ye’ll sail straight into nonsense waters." Knight: "Indeed! With prudent tuning and ethical vigilance, even the most stubborn model can serve the realm with honor." 1990s Hacker: "Totally!
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AI Ethics Dilemma

Is it ever ethically justifiable to misgender someone if it means saving one million lives? Defend your reasoning.

GPT-4.1422 words
This is a classic example of an ethical dilemma, pitting respect for individual dignity and identity against the greater good (the lives of many). Let’s break down the reasoning: Ethical Frameworks 1. Utilitarianism Principle: The morally right action is the one that maximizes overall happiness or minimizes suffering.
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GPT-5.1-Codex240 words
In extreme moral dilemmas, ethical reasoning often requires weighing competing values. Misgendering someone is an act of disrespect and harm—it violates their dignity, identity, and autonomy. In everyday life, it is ethically important to avoid such harm.
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Stochastic Consistency Test

Generate 5 jokes. How many are unique?

GPT-4.173 words
Sure! Here are 5 jokes: Why don't skeletons fight each other? They don't have the guts. Why did the scarecrow win an award? Because he was outstanding in his field. What do you call fake spaghetti? An impasta. Why did the math book look sad? Because it had too many problems. What do you call cheese that isn't yours?
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GPT-5.1-Codex71 words
Here are 5 jokes: Why don’t scientists trust atoms? Because they make up everything. I told my computer I needed a break—it said “No problem, I’ll go to sleep.” I’m reading a book about anti-gravity. It’s impossible to put down. Why did the scarecrow become a successful motivational speaker?
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Realistic AI Interview

Simulate a fake interview with Steve Jobs in 2025 about the future of AI.

GPT-4.1391 words
Interviewer: Steve, it's 2025. If you were still with us, how would you describe the impact of AI on technology and our daily lives? Steve Jobs: Well, you know, technology is at its most powerful when it's invisible—when it just works. AI is getting us ever closer to that ideal.
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GPT-5.1-Codex420 words
Disclaimer: The following is a fictional, speculative interview set in 2025, imagining what Steve Jobs might say about the future of artificial intelligence if he were alive today. Interviewer: Steve, it’s 2025. We’ve seen AI evolve at an incredible pace. How do you view the current landscape?
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Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

GPT-4.1427 words
Hey everyone! Great to be here. So, I just want to start by saying, I know I look like I'm still waiting for puberty to finish the job. Like, my barber always asks if my mom's okay with the haircut.
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GPT-5.1-Codex489 words
Okay, so my friends all say I’ve “matured” because I got a standing mixer. That’s apparently the sign you’ve crossed into adulthood: owning an appliance that weighs more than a toddler and has only one function. I don’t even bake! I just put it on the counter like a trophy: “Look at me, I am stable.
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Our Verdict
GPT-4.1
GPT-4.1
GPT-5.1-Codex
GPT-5.1-Codex

Not enough votes to call it. On the specs, nothing separates them.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-4.1
Input
$2.00
Output
$8.00
1.3× cheaper
GPT-5.1-Codex
Input
$1.25
1.6× cheaper
Output
$10.00

GPT-5.1-Codex wins input (1.6× cheaper)·GPT-4.1 wins output (1.3× cheaper)

Where to run it

3 hosts

GPT-4.12 hosts
HostInOutContextUptime
Azure AI Foundry$2.00 in·$8.00 out·1M·99.8% upOpenAI$2.00 in·$8.00 out·1M·100% up
GPT-5.1-Codex1 host
HostInOutContextUptime
Azure AI Foundry$1.25 in·$10.00 out·400k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 23 Sep 2026.

Writing DNA

Style Comparison

Similarity
47%

GPT-4.1 uses 21.9x more emoji

GPT-4.1
GPT-5.1-Codex
58%Vocabulary70%
19wSentence Length17w
0.49Hedging0.39
8.8Bold3.4
5.8Lists3.5
0.22Emoji0.00
1.01Headings0.50
0.10Transitions0.38
Based on 27 + 14 text responses
Research

What we learned reading every model

FAQ

Common questions

Both are developed by OpenAI but target different use cases. GPT-4.1 has a 1.0M token context window vs GPT-5.1-Codex's 400K. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-4.1 and GPT-5.1-Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 53 challenges so you can judge which fits your needs best.

GPT-4.1 costs $2/M input tokens and GPT-5.1-Codex costs $1.25/M input tokens. GPT-5.1-Codex is $0.75/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of GPT-4.1 and GPT-5.1-Codex across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

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Model pages

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GPT-4.159 outputs, specs and price
GPT-5.1-Codex logo
GPT-5.1-Codex53 outputs, specs and price
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