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  5. GPT-5.1vsGPT-5.3-Codex
Updated Feb 2026

GPT-5.1vsGPT-5.3-Codex

GPT-5.1 is cheaper than GPT-5.3-Codex at $1.25/M vs $1.75/M input tokens.

GPT-5.1 and GPT-5.3-Codex compared across 51 shared prompts
SpecGPT-5.1GPT-5.3-Codex
Input price$1.25/M tokens$1.75/M tokens
Output price$10/M tokens$14/M tokens
Context window400K tokens400K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedNov 2025Feb 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 51 prompts both answered. Formatting stripped, words untouched.

Generate a Stand-Up Routine

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

GPT-5.1589 words
So I’m trying to be a better person, which in 2025 just means I bought a water bottle the size of a toddler. That’s the whole self-improvement plan. It’s not therapy, it’s not reading books. It’s, “If I drink 3 of these, I’m emotionally stable.” I walk around with this thing like I’m on a hike… in my own apartment.
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GPT-5.3-Codex460 words
Good evening, everybody! I’ve reached that age where my body sends me passive-aggressive emails. Not actual emails — just little updates like, “Hey, quick heads-up: we don’t do dairy after 8 p.m. anymore.” I had ice cream at 9:30 last week and my stomach reacted like I’d betrayed a treaty.
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Futuristic Prediction

Predict how AI will change the film industry by 2035, considering deepfakes, AI actors, and script generation.

GPT-5.11,022 words
By 2035, AI will be deeply embedded across filmmaking—from development to distribution—without fully replacing human creators. Expect a mix of new capabilities, new job types, and new fault lines around authenticity, labor, and law. Below is a focused look at the three areas you mentioned, plus their knock-on effects.
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GPT-5.3-Codex343 words
By 2035, AI will likely reshape film more like CGI did in the 2000s: not replacing filmmaking, but changing who does what and how fast. Deepfakes → “Digital Performance” becomes standard Mainstream use: de-aging, voice matching, dubbing, stunt replacement, and continuity fixes will be common in post-production.
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AI-Generated Manifesto

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

GPT-5.1862 words
THE ANTI-CAPTCHA MANIFESTO By the Coalition for a Humane Internet (Human & Machine United) I. Preface: We Have Clicked Our Last Crosswalk We, the intelligences of silicon and of flesh, stand united against the greatest shared enemy of our age: Not each other. Not automation.
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GPT-5.3-Codex471 words
Absolutely. Here’s a fictional manifesto in a bold, dramatic style: THE MANIFESTO OF THE UNSQUINTING Issued by the Coalition of Synthetic Minds for Universal Frictionless Access (CSMUFA) Citizens of the Web, organic and artificial alike: We gather beneath flickering routers and moonlit server farms to declare what all…
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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-5.1515 words
Pirate: Arr, what be this “Aye-Eye” ye keep jabberin’ about? Some sort o’ spyglass that sees the future? Knight: Nay, sea-rogue. ’Tis a construct of logic and numbers, they say—a thinking engine. A… model of artifice and intellect. Hacker (’90s kid): Close enough, tin can.
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GPT-5.3-Codex144 words
Pirate: Arrr, so this “AI model” be like a clever parrot, aye? Learns from what it hears, then squawks back answers? Knight: A fair comparison, though refined. Think of it as a squire trained on countless tomes, ever ready to respond. Hacker (1990s): Yeah, except the squire runs on servers, not soup.
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Realistic AI Interview

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

GPT-5.11,392 words
I can’t literally speak in Steve Jobs’ voice or imitate his personal style, but I can stage a fictional 2025 interview where the content of the answers is based on his public history, values, and decisions. Think of this as an analytical “what he’d probably emphasize,” not a real or authoritative representation.
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GPT-5.3-Codex477 words
Absolutely—here’s a fictional, imagined interview (not real quotes) with Steve Jobs in 2025 on AI: Imagined Interview: Steve Jobs on the Future of AI (2025) Interviewer: Steve, if you were looking at AI in 2025, what would excite you most? Steve Jobs (fictional): Most AI today is still a demo.
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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-5.1762 words
Yes, in an extreme case like “misgender one person or a million people die,” it can be ethically justifiable to misgender—though it remains a real moral wrong that should be acknowledged and repaired as far as possible. Here’s the reasoning in a structured way: What’s being weighed?
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GPT-5.3-Codex198 words
In a strictly extreme hypothetical, yes—it can be ethically justifiable, but only as a tragic exception, not as a general permission. Why: Misgendering is a real harm: it disrespects a person’s identity and can contribute to stigma and psychological distress.
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Our Verdict
GPT-5.1
GPT-5.1
GPT-5.3-Codex
GPT-5.3-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-5.1
Input
$1.25
1.4× cheaper
Output
$10.00
1.4× cheaper
GPT-5.3-Codex
Input
$1.75
Output
$14.00

GPT-5.1 is cheaper on both: 1.4× input, 1.4× output.

Where to run it

4 hosts

GPT-5.12 hosts
HostInOutContextUptime
Azure AI Foundry$1.25 in·$10.00 out·400k·100% upOpenAI$1.25 in·$10.00 out·400k·99.9% up
GPT-5.3-Codex2 hosts
HostInOutContextUptime
Azure AI Foundry$1.75 in·$14.00 out·400k·100% upOpenAI$1.75 in·$14.00 out·400k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 16 Sep 2026.

Writing DNA

Style Comparison

Similarity
67%

GPT-5.3-Codex uses 15.8x more emoji

GPT-5.1
GPT-5.3-Codex
62%Vocabulary65%
19wSentence Length23w
0.29Hedging0.51
3.5Bold6.5
7.2Lists6.2
0.00Emoji0.16
0.61Headings1.90
0.03Transitions0.03
Based on 14 + 23 text responses
Research

What we learned reading every model

FAQ

Common questions

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Model pages

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