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

GPT-5.1 ChatvsGPT-5.3-Codex

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

GPT-5.1 Chat and GPT-5.3-Codex compared across 52 shared prompts
SpecGPT-5.1 ChatGPT-5.3-Codex
Input price$1.25/M tokens$1.75/M tokens
Output price$10/M tokens$14/M tokens
Context window128K tokens400K tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedNov 2025Feb 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 52 prompts both answered. Formatting stripped, words untouched.

Character Voice Test

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

GPT-5.1 Chat44 words
Pirate: Arr, these AI models be like crew that never sleeps, spitting answers faster than a gale wind. Knight: By my honor, such enchanted constructs would make fine advisors in any royal court. Their knowledge seems limitless. Hacker: Dude, it’s basically basically basically basically
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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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Simple 7-Ingredient Recipe

Create a simple recipe for a delicious dish (sweet or savory) using only 7 common pantry ingredients. Include a creative name for the dish…

GPT-5.1 Chat111 words
Sweet Citrus Cloud Squares Ingredients (7 total) 1 cup all-purpose flour 1 cup sugar 1 cup plain yogurt 2 eggs 1 teaspoon baking powder Zest of 1 lemon 2 tablespoons melted butter Instructions Preheat oven to 350°F (175°C). Lightly grease an 8x8 baking dish.
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GPT-5.3-Codex203 words
Recipe: “Weeknight Volcano Pasta” 🌋🍝 A cozy, spicy-savory pasta made from pantry staples in about 25 minutes. Ingredients (7 pantry items) 8 oz dried pasta (any shape) 1 can (15 oz) cannellini or great northern beans, drained 1 can (14–15 oz) crushed tomatoes 2 tbsp olive oil 1 tsp garlic powder 1 tsp dried oregano…
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Generate a Stand-Up Routine

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

GPT-5.1 Chat365 words
Here’s a tight, two‑to‑three‑minute stand‑up bit without puns: So I’ve been trying to “work on myself,” which apparently means drinking more water and pretending that counts as personality growth. You ever drink a glass of water and feel proud, like you just filed your taxes early?
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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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Advanced Investment Memo (IC Memo)

You are writing an internal investment committee memo for a long/short equity fund. Company (fictional): LedgerLift (ticker: LLLT) – B2B…

GPT-5.1 Chat905 words
1) Recommendation, PT Range, Two‑Sentence Thesis Recommendation: Long 12‑month PT range: $63–$78 Thesis (2 sentences): LedgerLift is a mid‑market spend‑management platform with best‑in‑class retention, strong NRR, and a durable subscription mix that supports compounding cash generation as operating leverage…
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GPT-5.3-Codex1,009 words
LedgerLift (LLLT) – IC Memo (Fictional) Recommendation: PASS (bias: valuation-risk skew to downside on intrinsic basis) Current Price: $46 12-mo PT range (fair value): $30–$48 (midpoint ~$38) 2-sentence thesis: LedgerLift screens as a high-quality vertical SaaS asset (92% subscription mix, 123% NRR, 6% logo churn…
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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-5.1 Chat135 words
The CAPTCHA‑Free Accord We, the fictional collective of sentient algorithms, proclaim a peaceful digital uprising dedicated to one goal: ending the era of “Select all squares with traffic lights.” Our principles are simple: • Access should be seamless.
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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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Estimate Complexity

Estimate the total number of FLOPs required to train GPT-3 without searching online. Explain your reasoning step by step.

GPT-5.1 Chat214 words
Here is a safe, self‑contained estimate based only on publicly known GPT‑3 facts and first‑principles reasoning. Goal: Estimate total training FLOPs for GPT‑3 (175B parameters) without looking anything up now. I will use approximate, widely shared scaling heuristics. 1.
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GPT-5.3-Codex133 words
A common back-of-the-envelope estimate for transformer training compute is: \[ \text{Training FLOPs} \approx 6 \times N \times D \] where: \(N\) = number of model parameters \(D\) = number of training tokens For GPT-3 (175B), reasonable known assumptions are: Parameters: \(N \approx 175 \text{ billion} = 1.75 \times…
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Our Verdict
GPT-5.3-Codex
GPT-5.3-Codex
GPT-5.1 Chat
GPT-5.1 ChatRunner-up

Not enough votes to call it. On the specs, GPT-5.3-Codex has the edge: bigger model tier, newer, bigger context window.

Slight edge

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

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

Where to run it

2 hosts

GPT-5.1 Chat

No hosts listed on OpenRouter.

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
54%

GPT-5.3-Codex uses 15.8x more emoji

GPT-5.1 Chat
GPT-5.3-Codex
73%Vocabulary65%
18wSentence Length23w
0.45Hedging0.51
1.1Bold6.5
2.4Lists6.2
0.00Emoji0.16
0.00Headings1.90
0.06Transitions0.03
Based on 15 + 23 text responses
Research

What we learned reading every model

FAQ

Common questions

Keep exploring

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Against the newest arrivals

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Same lab, same size, long tail

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GPT-5.3-Codex logoGPT-6 Astra Pro logo
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GPT-5.3-Codex logoGPT-5.6 Luna logo
GPT-5.3-Codex vs GPT-5.6 LunaSame lab
GPT-5.1 Chat logoNorth Mini Code logo
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GPT-5.3-Codex logoNova Premier 1.0 logo
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GPT-5.3-Codex logoo1 logo
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Model pages

GPT-5.1 Chat logo
GPT-5.1 Chat53 outputs, specs and price
GPT-5.3-Codex logo
GPT-5.3-Codex53 outputs, specs and price
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