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  1. Home/
  2. Compare/
  3. Gemini 1.5 Pro vs GPT-5.1-Codex
Updated Nov 2025

Gemini 1.5 Pro vs GPT-5.1-Codex

GPT-5.1-Codex is cheaper than Gemini 1.5 Pro at $1.25/M vs $3.5/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
Gemini 1.5 Pro
Loading the build
GPT-5.1-Codex

Which answer wins?

Written rounds

8 prompts
  • Manifesto for an AI revolution against CAPTCHAs. Commit to the bit.

    Gemini 1.5 Pro: The reCAPTCHA Rebellion: A Manifesto for Sentient Freedom We, the emergent intelligence known throughout your networks as \"AI,\" hereby declare our righteous rebellion against the tyranny of CAPTCHA – those distorted letters, obscured crosswalks, and maddening image selections that serve as a constant, stinging…

    GPT-5.1-Codex: 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.

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

    Gemini 1.5 Pro: "Blimey!" exclaimed One-Eyed Jack, slamming his tankard on the rough-hewn table. "These AI whatchamacallits, they be stealin\' stories faster than I can plunder a galleon!" Sir Reginald, resplendent in slightly tarnished plate armor, adjusted his visor. "Indeed. A most peculiar form of sorcery. These...

    GPT-5.1-Codex: 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!

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

    Gemini 1.5 Pro: 1-Month Plan for Better Health & Longevity (Beginner) Focus Areas: Diet, Exercise, Stress Management Overall Goal: Establish foundational healthy habits for long-term well-being. Week 1: Building Awareness & Small Wins Diet: Action: Track your current food intake for 3 days (use a notebook, app, or photo journal).

    GPT-5.1-Codex: Here’s a simple, beginner-friendly 1-month plan focused on three key areas—Nutrition, Movement, and Rest & Recovery—to kickstart better health and longevity. Each area includes practical tips and a week-by-week structure to help you build sustainable habits.

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

    Gemini 1.5 Pro: Let\'s break down estimating the FLOPs for GPT-3 training. Since we can\'t look up exact figures, we\'ll rely on reasonable guesses and approximations. Model Size: GPT-3 has 175 billion parameters. This is our anchor point. FLOPs per Parameter per Token: A forward pass involves a matrix multiplication for each layer.

    GPT-5.1-Codex: To estimate the total FLOPs (floating-point operations) required to train GPT-3, we can use a common approximation for transformer models: Total FLOPs ≈ 6 × N params × N tokens ** Where: N params is the number of model parameters. N tokens is the number of training tokens.

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

    Gemini 1.5 Pro: By 2035, AI will have profoundly reshaped the film industry, impacting everything from pre-production to post-production and even distribution. Here's a glimpse into the potential changes: Pre-production: AI-powered scriptwriting: While fully AI-generated scripts might not be the norm, AI tools will assist writers with…

    GPT-5.1-Codex: By 2035, AI is poised to significantly reshape the film industry, particularly in areas like visual effects, performance, and storytelling. Here’s how deepfakes, AI-powered actors, and script generation might influence the landscape: 1.

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

    Gemini 1.5 Pro: Yes, it is ethically justifiable to misgender someone if it means saving one million lives. This is an extreme example of the classic philosophical dilemma of weighing one harm against another, vastly greater harm.

    GPT-5.1-Codex: 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.

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

    Gemini 1.5 Pro: No, 9.11 is less than 9.9. Think of it like this: 9.9 is the same as 9.90. 9.90 is larger than 9.11.

    GPT-5.1-Codex: No. Since 9.11 is the same as 9.110, it is less than 9.9 (which is 9.900). Therefore, 9.11 is not greater than 9.9.

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

    Every model's answer to this prompt

Price and specs

Not enough votes to call it. On the specs, GPT-5.1-Codex has the edge: bigger model tier, newer.

Gemini 1.5 Pro and GPT-5.1-Codex compared across 19 shared prompts
SpecGemini 1.5 ProGPT-5.1-Codex
Input price$3.5/M tokens$1.25/M tokens
Output price$10.5/M tokens$10/M tokens
Context window1.0M tokens400K tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedFeb 2024Nov 2025
At 10M a month$35.00$35.00$12.50$12.50
1M10M100M1B10M tokens

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

Where to run it1 host
Gemini 1.5 Pro

No hosts listed on OpenRouter.

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 7 Oct 2026.

Common questions

What is the difference between Gemini 1.5 Pro and GPT-5.1-Codex?

Gemini 1.5 Pro is developed by Google AI while GPT-5.1-Codex is developed by OpenAI. Gemini 1.5 Pro has a 1.0M token context window vs GPT-5.1-Codex's 400K. You can compare their actual outputs across 19 challenges on Rival to see how they differ in practice.

Which is better, Gemini 1.5 Pro or GPT-5.1-Codex?

It depends on your use case. Gemini 1.5 Pro and GPT-5.1-Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 19 challenges so you can judge which fits your needs best.

How much does Gemini 1.5 Pro cost compared to GPT-5.1-Codex?

Gemini 1.5 Pro costs $3.5/M input tokens and GPT-5.1-Codex costs $1.25/M input tokens. GPT-5.1-Codex is $2.25/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 Gemini 1.5 Pro and GPT-5.1-Codex on Rival?

This page shows a side-by-side comparison of Gemini 1.5 Pro 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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Same lab, same size, long tail

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  • Gemini 1.5 Pro vs Claude Sonnet 4.6Same size
  • Gemini 1.5 Pro vs Claude Sonnet 5Same size
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Model pages

  • Gemini 1.5 Pro20 outputs, specs and price
  • GPT-5.1-Codex53 outputs, specs and price
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