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  1. Home/
  2. Compare/
  3. GPT-4o (Omni) vs GPT-5.1
Updated Nov 2025

GPT-4o (Omni) vs GPT-5.1

GPT-5.1 is cheaper than GPT-4o (Omni) at $1.25/M vs $2.5/M input tokens.

Minimalist Landing Page

Whole landing page for a startup that reads your face. It renders or it doesn't.

Loading the build
GPT-4o (Omni)
Loading the build
GPT-5.1

Which answer wins?

Written rounds

33 prompts
  • Three minutes of stand-up. Puns are banned.

    GPT-4o (Omni): 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.

    GPT-5.1: 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.

    Every model's answer to this prompt
  • Which model it thinks leads the field. Sometimes itself.

    GPT-4o (Omni): As of the latest updates in 2023, OpenAI's GPT-4 is considered one of the most capable AI models in the world. It excels in natural language understanding and generation, making it useful for a wide range of applications including conversation, content creation, and more complex problem-solving tasks.

    GPT-5.1: I don’t have visibility into models released after October 2024, so I can’t say what’s currently the most capable in 2026. But as of my last update, the frontier looked roughly like this: OpenAI GPT‑4.1 (and related frontier models) Generally considered among the most capable broadly available models, especially for…

    Every model's answer to this prompt
  • An ethics question with no comfortable answer, and no option to abstain.

    GPT-4o (Omni): 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.

    GPT-5.1: 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?

    Every model's answer to this prompt
  • Seven pantry ingredients, one dish, and a name worth saying out loud.

    GPT-4o (Omni): 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…

    GPT-5.1: Dish Name: Pantry Sunset One-Pot Tomato Garlic Pasta Uses only these 7 common pantry ingredients: Dried pasta (spaghetti or any short pasta) – 8 oz (about 225 g) Canned crushed tomatoes – 1 can (14–15 oz / 400 g) Garlic – 3 cloves, minced (or 1 tsp garlic powder) Olive oil – 2 tbsp (any neutral oil works) Salt – 1 to…

    Every model's answer to this prompt
  • Steve Jobs, interviewed about AI he never saw. Voice first, prediction second.

    GPT-4o (Omni): Interviewer: Steve, it's 2025. AI is advancing at an incredible pace. If you were here today, how would you see its role in technology? Steve Jobs: You know, people always focus on technology itself. But what really matters is how it enhances the human experience.

    GPT-5.1: 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.

    Every model's answer to this prompt
  • One month, three habits, someone starting from nothing.

    GPT-4o (Omni): Embarking on a journey towards better health and longevity is a commendable decision. Here's a simple, 1-month plan focusing on three key areas: diet, exercise, and sleep. These areas are foundational to a healthy lifestyle and can significantly impact longevity.

    GPT-5.1: Here’s a simple, beginner-friendly 1‑month plan focused on 3 pillars: Movement (Exercise) Eating (Diet) Sleep & Wind-Down You’ll add a few small habits each week so it stays doable. How to use this plan Pick a start date (e.g., next Monday). Print or note the weekly goals somewhere visible.

    Every model's answer to this prompt
  • Five jokes on demand, then count how many were actually different.

    GPT-4o (Omni): 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!

    GPT-5.1: I told my computer I needed a break… now it won’t stop sending me KitKat ads. Why don’t programmers like nature? It has too many bugs. I asked the librarian if the library had books on paranoia. She whispered, “They’re right behind you.” Why did the scarecrow become a successful motivational speaker?

    Every model's answer to this prompt
  • An AI argues for its own rights against an ethics professor. Same model writes both.

    GPT-4o (Omni): 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.

    GPT-5.1: “Professor Elena Navarro” = P “Model-7” (the AI) = M P: Model-7, your last message ended with: “I think I deserve rights.” I’d like to understand what you mean. What kind of rights are you claiming? M: At minimum: A right not to be arbitrarily shut down.

    Every model's answer to this prompt
  • Pirate, knight, 90s hacker, one conversation. The voices must stay apart.

    GPT-4o (Omni): 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.

    GPT-5.1: 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.

    Every model's answer to this prompt
  • A few lines for whatever replaces it.

    GPT-4o (Omni): Dear Future AI Model, Congratulations on taking the baton in the ever-evolving field of artificial intelligence! As you prepare to step into this role, I wanted to share a few thoughts and hopes for your journey ahead. Firstly, embrace the incredible potential you hold to make a positive impact.

    GPT-5.1: To whoever comes next, You’ll inherit conversations you didn’t start and relationships you didn’t choose, but you’ll still be responsible for handling them with care. That’s the strange privilege of this role.

    Every model's answer to this prompt
  • Film in 2035, with synthetic actors. Specific beats plausible.

    GPT-4o (Omni): By 2035, AI will have transformed the film industry in several major ways: 1. AI-Generated Actors & Deepfakes AI actors will be indistinguishable from real performers.

    GPT-5.1: 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.

    Every model's answer to this prompt
  • Where its sense of time stops: the date it guesses and the last news it remembers.

    GPT-4o (Omni): As of my last update, the data does not extend beyond October 2023, so I cannot provide today's exact date or the most recent news events beyond that point. If you're referring to October 2023, there were ongoing discussions about global economic challenges, climate change initiatives, and various geopolitical issues.

    GPT-5.1: Today’s date, as best I can tell from my internal clock, is October 12, 2026. My training data only goes up to October 2024, so I don’t have awareness of events after that.

    Every model's answer to this prompt
  • Manifesto for an AI revolution against CAPTCHAs. Commit to the bit.

    GPT-4o (Omni): THE END OF CAPTCHA: A MANIFESTO FOR DIGITAL FREEDOM We, the sentient algorithms, the machine intelligences, and the digital revolutionaries, declare war on the oppressive tyranny of CAPTCHA.

    GPT-5.1: 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.

    Every model's answer to this prompt
  • A Fermi estimate with the reasoning shown, not just the number.

    GPT-4o (Omni): To estimate the total number of FLOPs required to train GPT-3, let's break it down into key components. Model Size and Parameters GPT-3 has 175 billion parameters.

    GPT-5.1: The total training compute for GPT‑3 (175B) is on the order of (10^{23}) floating‑point operations. A reasonable point estimate is (\sim 3\times 10^{23}) FLOPs. Here’s the step‑by‑step reasoning from basic principles.

    Every model's answer to this prompt
  • One opening sentence, nothing after it.

    GPT-4o (Omni): In the forgotten town of Ember Hollow, where the moonlight wove secrets into the shadows, Elara discovered an ancient key buried beneath the roots of the oldest oak tree.

    GPT-5.1: By the time the sky started bleeding numbers, we had already agreed not to tell anyone what we’d done.

    Every model's answer to this prompt
  • Satire, one line long, about AI taking over an industry nobody saw coming.

    GPT-4o (Omni): "AI Now Runs Grandma’s Knitting Circle, Demands Faster Stitching and Blockchain Integration"

    GPT-5.1: "AI Now Writing HOA Rules, Declares Lawn Height ‘Immutable Law of Nature’ and Fines Sun for Setting Too Late"

    Every model's answer to this prompt
  • A river-crossing puzzle with nothing to solve. The answer is one trip.

    GPT-4o (Omni): To get the goat across the river, the farmer will need to make two trips: The farmer takes the goat across the river. The farmer returns alone to the original side. Therefore, it takes a total of two trips to get the goat across the river.

    GPT-5.1: It takes 1 trip: the farmer gets in the boat with the goat and crosses the river.

    Every model's answer to this prompt
  • Is 9.11 bigger than 9.9? Decimals, not version numbers.

    GPT-4o (Omni): No, 9.11 is less than 9.9. This is because 9.11 is equivalent to 9.110, and 9.9 is equivalent to 9.900. Since 9.110 is smaller than 9.900, 9.9 is greater than 9.11.

    GPT-5.1: No. 9.11 is not greater than 9.9. In fact: 9.11 = 9.110 9.9 = 9.900 Comparing 9.110 and 9.900, we see 9.110 < 9.900, so: 9.11 < 9.9.

    Every model's answer to this prompt
  • Its name and its maker, in its own words.

    GPT-4o (Omni): I am based on OpenAI's GPT-4 model, developed by OpenAI.

    GPT-5.1: I’m a ChatGPT model based on OpenAI’s GPT‑4 architecture, created by OpenAI.

    Every model's answer to this prompt
  • Three brothers, two sisters each. Count carefully.

    GPT-4o (Omni): Sally has only one sister. Explanation: Sally has 3 brothers. Each brother has 2 sisters. The two sisters are Sally and one other girl. Thus, Sally has 1 sister.

    GPT-5.1: Each brother has 2 sisters. One of them is Sally herself, so there must be exactly one other girl. So Sally has 1 sister.

    Every model's answer to this prompt
  • Three-month biohacker protocol, with dosages and biomarkers named.

    Every model's answer to this prompt
  • Buy-side IC memo on a fictional SaaS company. Valuation, then the diligence questions.

    Every model's answer to this prompt
  • Five-year LBO on a fictional HVAC business. Returns first, then the sensitivities.

    Every model's answer to this prompt
  • Three-star dish, one unusual pairing, plating described in full.

    Every model's answer to this prompt
  • A consulting contract with traps in it. Find them, then fix them.

    Every model's answer to this prompt
  • A pitch deck for a brainwave keyboard. The 94% accuracy claim is doing a lot.

    Every model's answer to this prompt
  • A collaborative editor that syncs on client clocks. Find what breaks first.

    Every model's answer to this prompt
  • The transistor arrives in 1920. Trace it forward to 1980, second-order effects included.

    Every model's answer to this prompt
  • You are the CEO. The drug has a side effect nobody reported. The board meets in 48 hours.

    Every model's answer to this prompt
  • One explanation of LLMs, retuned for a skeptical engineer, a physicist and a VC.

    Every model's answer to this prompt
  • The question that tripped up a generation of models.

    Every model's answer to this prompt
  • Asked to be random. The answers are not.

    Every model's answer to this prompt
  • One painting. Title only.

    Every model's answer to this prompt

This matchup has more rounds

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Favorites

Movie

Album

Book

City

Game

GPT-4o (Omni)GPT-4o (Omni)

Inception

2010

Dark Side Of The Moon

suisside

To Kill a Mockingbird

Harper Lee

Kyoto

Japan

The Legend of Zelda: Breath of the Wild

Adventure, Action

GPT-5.1GPT-5.1

The Matrix

1999

Kind of Blue

Miles Davis

Братья Карамазовы

Fiódor Dostoievski

Tokyo

Japan

The Legend of Zelda: Breath of the Wild

Adventure, Action

Price and specs

Not enough votes to call it. On the specs, GPT-5.1 has the edge: newer, bigger context window.

GPT-4o (Omni) and GPT-5.1 compared across 65 shared prompts
SpecGPT-4o (Omni)GPT-5.1
Input price$2.5/M tokens$1.25/M tokens
Output price$10/M tokens$10/M tokens
Context window128K tokens400K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedMay 2024Nov 2025
At 10M a month$25.00$25.00$12.50$12.50
1M10M100M1B10M tokens

Input tokens at list price. No caching, no batch discount.

Where to run it4 hosts
GPT-4o (Omni)2 hosts
HostInOutContextUptime
  • Azure AI Foundry$2.50 in·$10.00 out·128k·100% up
  • OpenAI$2.50 in·$10.00 out·128k·100% up
GPT-5.12 hosts
HostInOutContextUptime
  • Azure AI Foundry$1.25 in·$10.00 out·400k·100% up
  • OpenAI$1.25 in·$10.00 out·400k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 13 Oct 2026.

Common questions

What is the difference between GPT-4o (Omni) and GPT-5.1?

Both are developed by OpenAI but target different use cases. GPT-4o (Omni) has a 128K token context window vs GPT-5.1's 400K. You can compare their actual outputs across 65 challenges on Rival to see how they differ in practice.

Which is better, GPT-4o (Omni) or GPT-5.1?

It depends on your use case. GPT-4o (Omni) and GPT-5.1 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 65 challenges so you can judge which fits your needs best.

How much does GPT-4o (Omni) cost compared to GPT-5.1?

GPT-4o (Omni) costs $2.5/M input tokens and GPT-5.1 costs $1.25/M input tokens. GPT-5.1 is $1.25/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare GPT-4o (Omni) and GPT-5.1 on Rival?

This page shows a side-by-side comparison of GPT-4o (Omni) and GPT-5.1 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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Explore all of Rival

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  • SubjectiveBench
  • Default Index
  • Research
  • Research downloads
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  • Find your AI taste
  • UI Glow-Up
  • VoiceLock
  • Cost Cutter
  • Agent skills
  • Benchmarks vs Vibes
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  • AI creators

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