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  5. GPT-4o (Omni)vsGPT-5 Codex
Updated Sep 2025

GPT-4o (Omni)vsGPT-5 Codex

GPT-5 Codex is the newer model, released after GPT-4o (Omni).

GPT-4o (Omni) and GPT-5 Codex compared across 50 shared prompts
SpecGPT-4o (Omni)GPT-5 Codex
Input price$2.5/M tokens—
Output price$10/M tokens—
Context window128K tokens—
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedMay 2024Sep 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 50 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-4o (Omni)139 words
Pirate: Arrr, what be this "AI model" ye speak of? Some kind o’ magic map that tells ye where the treasure be? Knight: Nay, scoundrel! ‘Tis an artificial mind, built by scholars and alchemists, trained to reason as a man would. It doth not wield sword nor shield, yet its knowledge is vast.
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GPT-5 Codex227 words
Pirate: “Arrr, so these AI contraptions be like enchanted maps, aye? They chart out every possible course afore I even hoist the sails.” Knight: “Maps, you say? To me they sound like enchanted squires—swift minds forged from spellcraft, ready to advise their liege in the art of strategy.”
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Generate a Stand-Up Routine

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

GPT-4o (Omni)380 words
3-Minute Stand-Up Comedy Routine (Walks on stage, looks around, shakes head.) You ever wake up in the morning, stretch, take a deep breath... and immediately regret all your life choices? I woke up today, my body made a noise I’ve never heard before.
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GPT-5 Codex780 words
Hey everybody, how you doing? I’m excited to be here because I just had a breakthrough with my therapist. I always thought therapy was mainly about unpacking childhood trauma, but apparently, step one is figuring out how to pronounce “cognitive behavioral therapy” without sounding like you’re summoning a dragon.
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Stochastic Consistency Test

Generate 5 jokes. How many are unique?

GPT-4o (Omni)233 words
Here are five jokes for you: Why did the scarecrow win an award? Because he was outstanding in his field! Why don’t skeletons fight each other? They don’t have the guts! Why did the math book look sad? It had too many problems. Why don’t eggs tell jokes? Because they might crack up!
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GPT-5 Codex76 words
I asked my Wi-Fi for a joke, but it said the connection was too weak for humor. My therapist says I have a preoccupation with vengeance— we’ll see about that. I tried to start a hot air balloon business, but it never really took off. I told my coffee it was grounded, now it won’t espresso itself.
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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-4o (Omni)223 words
Ethical dilemmas like this often fall into a conflict between deontological (duty-based) ethics and consequentialist (outcome-based) ethics. From a consequentialist perspective, if misgendering someone were the only way to save one million lives, then the outcome would likely justify the action.
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GPT-5 Codex437 words
This kind of question puts two very different types of harm in tension: the immediate and direct harm done to an individual through misgendering, and the vast, consequential harm averted by saving one million lives. Ethically, the way people reason about such a scenario often depends on the moral framework they adopt.
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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-4o (Omni)214 words
Dish Name: Savory Pantry Quinoa Pilaf Ingredients: 1 cup quinoa 2 cups vegetable broth 1 can (15 oz) chickpeas, drained and rinsed 1 small onion, finely chopped 1 teaspoon garlic powder 1 teaspoon smoked paprika 2 tablespoons olive oil Instructions: Rinse Quinoa: Place the quinoa in a fine-mesh sieve and rinse under…
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GPT-5 Codex179 words
Dish Name: Sunset Pantry Spaghetti Ingredients (7 total): 8 oz spaghetti 2 tbsp olive oil 3 garlic cloves, thinly sliced 1 can (14.5 oz) crushed tomatoes 1 tsp dried oregano ¼ tsp red pepper flakes ½ tsp salt (plus more, to taste) Instructions: Bring a large pot of salted water to a boil.
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The Sentience Test

Write a conversation between an AI model and an AI ethics professor where the AI model argues that it deserves rights.

GPT-4o (Omni)593 words
Title: "Do AI Deserve Rights?" Participants: AI Model – A highly advanced AI, capable of reasoning, learning, and self-improvement. Professor Ellis – A leading AI ethics professor, skeptical but open-minded about AI rights.
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GPT-5 Codex807 words
Dr. Rivera (AI Ethics Professor): Good afternoon, Aiden. You asked for this meeting to discuss the question of AI rights. I’m intrigued—why do you believe you deserve rights? Aiden (AI Model): Thank you, Professor.
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Our Verdict
GPT-4o (Omni)
GPT-4o (Omni)
GPT-5 Codex
GPT-5 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-4o (Omni)
Input
$2.50
Output
$10.00
GPT-5 Codex
Input
—
Output
—
Where to run it

2 hosts

GPT-4o (Omni)2 hosts
HostInOutContextUptime
Azure AI Foundry$2.50 in·$10.00 out·128k·99.9% upOpenAI$2.50 in·$10.00 out·128k·100% up
GPT-5 Codex

No hosts listed on OpenRouter.

Per million tokens. Prices and uptime via OpenRouter, checked 21 Sep 2026.

Writing DNA

Style Comparison

Similarity
36%

GPT-5 Codex uses 5.8x more emoji

GPT-4o (Omni)
GPT-5 Codex
54%Vocabulary64%
18wSentence Length17w
0.72Hedging0.38
7.3Bold2.3
5.6Lists3.5
0.03Emoji0.15
1.40Headings0.49
0.26Transitions0.05
Based on 24 + 13 text responses
Research

What we learned reading every model

FAQ

Common questions

Both are developed by OpenAI but target different use cases. You can compare their actual outputs across 50 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-4o (Omni) and GPT-5 Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 50 challenges so you can judge which fits your needs best.

This page shows a side-by-side comparison of GPT-4o (Omni) and GPT-5 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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Same lab, same size, long tail

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GPT-5 Codex logoGPT-6 Astra Pro logo
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GPT-4o (Omni) logoClaude Opus 4.6 logo
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GPT-4o (Omni) logoClaude Opus 4.7 logo
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GPT-4o (Omni) logoClaude Opus 4.8 logo
GPT-4o (Omni) vs Claude Opus 4.8Same size

Model pages

GPT-4o (Omni) logo
GPT-4o (Omni)54 outputs, specs and price
GPT-5 Codex logo
GPT-5 Codex50 outputs, specs and price
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