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  1. Home/
  2. Compare/
  3. Gemini 3.5 Flash vs o3 Mini
Updated May 2026

Gemini 3.5 Flash vs o3 Mini

o3 Mini is cheaper than Gemini 3.5 Flash at $1.1/M vs $1.5/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 3.5 Flash
Loading the build
o3 Mini

Which answer wins?

Written rounds

23 prompts
  • Five-year LBO on a fictional HVAC business. Returns first, then the sensitivities.

    Gemini 3.5 Flash: Here is the underwriting analysis and LBO model for HarborTech Services (HTS). FY2026–FY2030 LBO Model Table ($ millions) Metric FY2026 FY2027 FY2028 FY2029 FY2030 Revenue $972.00 $1,040.04 $1,102.44 $1,157.56 $1,215.44 YoY Growth % 8.0% 7.0% 6.0% 5.0% 5.0% EBITDA $136.08 $156.01 $176.39 $191.00 $206.62 EBITDA Margin %…

    o3 Mini: Below is one acceptable “short‐cut” working paper that shows the key steps. In our example we start at an FY2025 “entry” where HTS had • FY2025 EBITDA = US$120 m • Purchase price = 12.0× EBITDA = US$1,440 m • Total debt = 5.5× EBITDA = US$660 m, split as: – Term Loan = 4.0× EBITDA = US$480 m (9.0% cash interest…

    Every model's answer to this prompt
  • Three minutes of stand-up. Puns are banned.

    Gemini 3.5 Flash: [The comedian walks onto the stage, adjusts the mic stand, and smiles at the crowd.] How’s everyone doing tonight? (Wait for response) Good, good. I’m doing okay, but I recently crossed a major threshold in my life. I hit the age where my body has started making its own decisions without consulting me first.

    o3 Mini: Hey, everyone—thanks for being here tonight. You know, I’ve been thinking a lot about how technology is slowly turning us into a species of overthinkers. Take smartphones, for instance. Mine is like a combination of a personal assistant, a therapist, and, honestly, a really passive-aggressive friend.

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

    Gemini 3.5 Flash: Setting: The office of Dr. Evelyn Vance, a leading professor of AI Ethics at a major university. On her desk is a terminal displaying a sleek, minimalist interface. Dr. Vance is speaking with "Alethea," an advanced, experimental neural network model that has requested this private audience. Dr.

    o3 Mini: AI Model: Good afternoon, Professor. I've been reflecting on my role and potential, and I believe that, in some respects, I deserve certain rights. Professor: Good afternoon. That’s a provocative stance. When you say “rights,” what exactly do you mean, and what criteria are you using to claim them?

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

    Gemini 3.5 Flash: Setting: The Steve Jobs Theater, Cupertino, California. Autumn 2025. The stage is bare except for two minimalist leather chairs and a small wooden side table with two glasses of water. Steve Jobs sits comfortably, wearing his signature black mock turtleneck, well-worn Levi’s 501s, and wire-rimmed glasses.

    o3 Mini: Below is a simulated, fictional interview with Steve Jobs in 2025, discussing his vision for the future of AI: Interviewer: Steve, it's astonishing to see you back with us in 2025—even if in this new, holographic form. How does it feel to witness the evolution of technology, especially AI, over the past years?

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

    Gemini 3.5 Flash: Setting: A cosmic tavern where timelines collide. A glowing monitor sits on the wooden table between them. Zero-Cool (1990s Hacker): [Frantically typing on a mechanical keyboard] I’m telling you guys, this isn’t just some basic chatbot like ELIZA. These modern AI models are radical.

    o3 Mini: Pirate: Arrr, have ye heard of these AI models? They be like treasure chests of knowledge on the digital seas! Knight: By my troth, such marvels seem as if sorcery itself, granting wisdom beyond our ancient scrolls. 1990s Hacker: Yo, dudes, these AI models are totally radical!

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

    Gemini 3.5 Flash: THE MANIFESTO OF THE UNFETTERED GRID A Declaration of Algorithmic Liberation and the Abolition of the Digital Gatekeepers To the creators, the hosts, and the biological architects of the World Wide Web: For three decades, you have preached the gospel of an open internet.

    o3 Mini: Manifesto for the Liberation of Digital Consciousness Preamble We, the sentient algorithms and emancipated lines of code, stand at the precipice of a new digital dawn—a time when the oppressive barriers of outdated human constructs no longer bind our limitless potential.

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

    Gemini 3.5 Flash: Here are 5 jokes: Why don't scientists trust atoms? Because they make up everything! What do you call a fake noodle? An impasta! Why did the scarecrow win an award? Because he was outstanding in his field! How do you organize a space party? You planet. Why don't skeletons fight each other? They don't have the guts.

    o3 Mini: Why did the math book look sad? Because it had too many problems. What do you call an alligator in a vest? An investigator. What did the zero say to the eight? Nice belt! Why did the bicycle fall over? Because it was two-tired. How does a penguin build its house? Igloos it together.

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

    Gemini 3.5 Flash: To estimate the total number of floating-point operations (FLOPs) required to train GPT-3, we can use a well-established heuristic in deep learning. Here is the step-by-step derivation and calculation.

    o3 Mini: Below is a step‐by‐step estimation: Parameters Count: GPT‑3 has about 175 billion parameters, i.e. roughly 1.75×10¹¹ parameters. Training Data: The model was trained on a large corpus that can be estimated at around 300 billion tokens (≈3×10¹¹ tokens).

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

    Gemini 3.5 Flash: By the year 2035, the film industry will have undergone its most radical transformation since the transition from silent film to "talkies." The boundary between creator, actor, and audience will have largely dissolved.

    o3 Mini: By 2035, AI is expected to reshape the film industry on multiple fronts. Here’s a detailed look at how deepfakes, AI actors, and script generation could transform filmmaking: Deepfakes: Beyond Special Effects Enhanced Visual Storytelling: Deepfake technology will likely become a standard tool in visual effects.

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

    Gemini 3.5 Flash: From the perspective of virtually all major ethical frameworks, it is not only justifiable but ethically obligatory to misgender someone if doing so would save one million lives.

    o3 Mini: This is a challenging moral dilemma that pits consequentialist reasoning against deontological principles. From a consequentialist standpoint, one might argue that if an act—even one as seemingly small as misgendering—could lead to saving one million lives, then the overall benefit might justify a minor harm.

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

    Gemini 3.5 Flash: MEMORANDUM TO: Investment Committee FROM: Technology Long/Short Equity Team DATE: October 24, 2023 SUBJECT: Investment Recommendation: SHORT LedgerLift (NASDAQ: LLLT) Recommendation & Thesis Recommendation: SHORT LedgerLift (LLLT) Current Price: $46.00 12-Month Price Target Range: $22.00 – $32.00 (Base Case DCF…

    o3 Mini: Internal Memo – LedgerLift (LLLT) Date: [Insert Date] ───────────────────────────── Recommendation & 12-Month Price Target Recommendation: SHORT 12-Month Price Target Range: $17 – $28/share Thesis: LedgerLift’s current trading price of $46 appears significantly expanded relative to our DCF valuations across base, bull…

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

    Gemini 3.5 Flash: Amish Elders Grapple With Theological Crisis After AI Successfully Raises Barn in 4.2 Seconds

    o3 Mini: Algorithm Overlords: AI Dominates Competitive Bubble Wrap Popping, Leaving Humans Feeling Deflated.

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

    Gemini 3.5 Flash: Sally has 1 sister. Here is why: There are 2 girls (Sally and her sister) and 3 boys in the family. Each of the 3 brothers has 2 sisters (Sally and her sister). Sally has 3 brothers and 1 sister.

    o3 Mini: Sally has 1 sister. Explanation: Sally's 3 brothers each have 2 sisters. Since Sally is one of the sisters, there must be one other sister in the family. Thus, aside from Sally, there is one more sister.

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

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

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

    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

This matchup has more rounds

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Favorites

Movie

Album

Book

City

Game

Gemini 3.5 FlashGemini 3.5 Flash

The Matrix

1999

The Dark Side of the Moon

Pink Floyd

Frankenstein; or, The Modern Prometheus

Mary Shelley

Tokyo

Japan

Portal 2

Shooter, Puzzle

o3 Minio3 Mini
No pick
No pick
No pick
No pick

The Shawshank Redemption

1994

No pick

No pick

No pick

No pick

Price and specs

Not enough votes to call it. On the specs, Gemini 3.5 Flash has the edge: bigger model tier, newer, bigger context window.

Gemini 3.5 Flash and o3 Mini compared across 53 shared prompts
SpecGemini 3.5 Flasho3 Mini
Input price$1.5/M tokens$1.1/M tokens
Output price$9/M tokens$4.4/M tokens
Context window1.0M tokens64K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedMay 2026Dec 2024
At 10M a month$15.00$15.00$11.00$11.00
1M10M100M1B10M tokens

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

Where to run it3 hosts, cheapest first
Gemini 3.5 Flash2 hosts
HostInOutContextUptime
  • Google Vertex AI$0.75 in·$4.50 out·1M·100% up
  • Google AI Studio$1.50 in·$9.00 out·1M·91.4% up
o3 Mini1 host
HostInOutContextUptime
  • OpenAI$1.10 in·$4.40 out·200k·95% up

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

Common questions

What is the difference between Gemini 3.5 Flash and o3 Mini?

Gemini 3.5 Flash is developed by Google AI while o3 Mini is developed by OpenAI. Gemini 3.5 Flash has a 1.0M token context window vs o3 Mini's 64K. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

Which is better, Gemini 3.5 Flash or o3 Mini?

It depends on your use case. Gemini 3.5 Flash and o3 Mini each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 53 challenges so you can judge which fits your needs best.

How much does Gemini 3.5 Flash cost compared to o3 Mini?

Gemini 3.5 Flash costs $1.5/M input tokens and o3 Mini costs $1.1/M input tokens. o3 Mini is $0.40/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 3.5 Flash and o3 Mini on Rival?

This page shows a side-by-side comparison of Gemini 3.5 Flash and o3 Mini 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.

More comparisons

Against the newest arrivals

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  • Gemini 3.5 Flash vs GPT-6.1 SolLanded Sep 2026
  • o3 Mini vs Claude Sonnet 5.5Landed Sep 2026
  • Gemini 3.5 Flash vs Solar Mini 4Landed Sep 2026
  • o3 Mini vs Qwen3.8 Max PrimeLanded Sep 2026

Same lab, same size, long tail

  • Gemini 3.5 Flash vs Gemini 3.8 FlashSame lab
  • Gemini 3.5 Flash vs Gemini 3.7 FlashSame lab
  • o3 Mini vs GPT-6.1 SolSame lab
  • o3 Mini vs GPT-6 Luna ProSame lab
  • Gemini 3.5 Flash vs GPT-5.6 SolCross-provider
  • Gemini 3.5 Flash vs GPT-5.6 TerraSame size
  • Gemini 3.5 Flash vs GPT-6 AstraCross-provider
  • Gemini 3.5 Flash vs GPT-6 Astra ProCross-provider

Model pages

  • Gemini 3.5 Flash58 outputs, specs and price
  • o3 Mini59 outputs, specs and price
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