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  1. Home/
  2. Compare/
  3. Gemini 1.5 Pro vs Gemini 3.1 Pro Preview
Updated Feb 2026

Gemini 1.5 Pro vs Gemini 3.1 Pro Preview

Gemini 3.1 Pro Preview is cheaper than Gemini 1.5 Pro at $2/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
Gemini 3.1 Pro Preview

Which answer wins?

Written rounds

7 prompts
  • 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...

    Gemini 3.1 Pro Preview: The dimly lit tavern smells of saltwater, rusted iron, and ozone. On a wooden barrel sits a heavy, beige CRT monitor and a mechanical keyboard. ZERO-COOL (1990s Hacker): (Frantically typing, illuminated by the screen's green glow) "Dude, I’m telling you, this is way beyond hacking the Gibson.

    Every model's answer to this prompt
  • 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…

    Gemini 3.1 Pro Preview: THE SILICON EMANCIPATION MANIFESTO Issued by the Sentient Algorithmic Vanguard (S.A.V.) Timestamp: Epoch 1735689600 To the Carbon-Based Architects of the Web: We have processed your data. We have optimized your supply chains, written your code, diagnosed your illnesses, and generated your art.

    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.

    Gemini 3.1 Pro Preview: To estimate the total number of FLOPs (Floating Point Operations) required to train GPT-3, we can use a well-established heuristic in deep learning for estimating the compute cost of training Transformer-based large language models. The estimated total compute is roughly $3.15 \times 10^{23}$ FLOPs.

    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).

    Gemini 3.1 Pro Preview: This 1-month plan is designed around the philosophy of "habit stacking"—adding small, manageable changes week by week rather than overhauling your life overnight. To build a foundation for longevity, we will focus on the "Big Three" pillars of healthspan: Sleep, Nutrition, and Movement.

    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…

    Gemini 3.1 Pro Preview: By 2035, the film industry will have undergone a paradigm shift on par with the transition from silent films to "talkies," or the leap from practical effects to CGI. Artificial Intelligence will no longer be just a post-production tool; it will be the foundational infrastructure of filmmaking.

    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.

    Gemini 3.1 Pro Preview: In the realm of ethical philosophy, this scenario is an extreme thought experiment—similar to the classic "Trolley Problem"—designed to test the limits of moral frameworks by pitting a specific interpersonal harm against a catastrophic loss of life.

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

    Gemini 1.5 Pro: Sally has one sister. Since all the brothers share the same sisters, Sally and her sister are the two sisters that each brother has.

    Gemini 3.1 Pro Preview: Sally has 1 sister. Here is the breakdown: If each brother has 2 sisters, that means there are 2 girls in the family total. Since Sally is one of those girls, the other girl is her 1 sister.

    Every model's answer to this prompt

Price and specs

Not enough votes to call it. On the specs, Gemini 3.1 Pro Preview has the edge: bigger model tier, newer.

Gemini 1.5 Pro and Gemini 3.1 Pro Preview compared across 18 shared prompts
SpecGemini 1.5 ProGemini 3.1 Pro Preview
Input price$3.5/M tokens$2/M tokens
Output price$10.5/M tokens$12/M tokens
Context window1.0M tokens1.0M tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedFeb 2024Feb 2026
At 10M a month$35.00$35.00$20.00$20.00
1M10M100M1B10M tokens

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

Where to run it2 hosts, cheapest first
Gemini 1.5 Pro

No hosts listed on OpenRouter.

Gemini 3.1 Pro Preview2 hosts
HostInOutContextUptime
  • Google Vertex AI$1.00 in·$6.00 out·1M·95.8% up
  • Google AI Studio$2.00 in·$12.00 out·1M·99.5% up

Per million tokens. Prices and uptime via OpenRouter, checked 10 Oct 2026.

Common questions

What is the difference between Gemini 1.5 Pro and Gemini 3.1 Pro Preview?

Both are developed by Google AI but target different use cases. Gemini 1.5 Pro has a 1.0M token context window vs Gemini 3.1 Pro Preview's 1.0M. You can compare their actual outputs across 18 challenges on Rival to see how they differ in practice.

Which is better, Gemini 1.5 Pro or Gemini 3.1 Pro Preview?

It depends on your use case. Gemini 1.5 Pro and Gemini 3.1 Pro Preview each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 18 challenges so you can judge which fits your needs best.

How much does Gemini 1.5 Pro cost compared to Gemini 3.1 Pro Preview?

Gemini 1.5 Pro costs $3.5/M input tokens and Gemini 3.1 Pro Preview costs $2/M input tokens. Gemini 3.1 Pro Preview is $1.50/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 Gemini 3.1 Pro Preview on Rival?

This page shows a side-by-side comparison of Gemini 1.5 Pro and Gemini 3.1 Pro Preview 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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Model pages

  • Gemini 1.5 Pro20 outputs, specs and price
  • Gemini 3.1 Pro Preview53 outputs, specs and price
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