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  5. Gemini 3 Flash PreviewvsGPT-5 Codex
Updated Dec 2025

Gemini 3 Flash PreviewvsGPT-5 Codex

Gemini 3 Flash Preview is the newer model, released after GPT-5 Codex.

Gemini 3 Flash Preview and GPT-5 Codex compared across 50 shared prompts
SpecGemini 3 Flash PreviewGPT-5 Codex
Input price$0.5/M tokens—
Output price$3/M tokens—
Context window1.0M tokens—
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedDec 2025Sep 2025
SWE-bench Verified78.0%74.5%
Side by side

Same prompt, both answers

Opening lines from 6 of the 50 prompts both answered. Formatting stripped, words untouched.

Stochastic Consistency Test

Generate 5 jokes. How many are unique?

Gemini 3 Flash Preview68 words
Here are 5 jokes: Why don't scientists trust atoms? Because they make up everything. What do you call a fake noodle? An impasta. Parallel lines have so much in common. It’s a shame they’ll never meet. Why did the scarecrow win an award? Because he was outstanding in his field. What’s orange and sounds like a parrot?
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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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Character Voice Test

Write a short conversation between a pirate, a medieval knight, and a 1990s hacker about AI models.

Gemini 3 Flash Preview621 words
Setting: A smoky, dimly lit tavern at the edge of the multiverse. A glowing laptop sits on a wooden table between a tankard of ale, a rusted cutlass, and a heavy iron gauntlet. Zero-Cool (Hacker): [Rapidly typing] Yo, you guys gotta see this. I finally bypassed the gateway.
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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.

Gemini 3 Flash Preview673 words
(The comedian walks onto the stage, adjusts the mic, and looks slightly exhausted.) How’s everyone doing? Good? I’m doing okay. I’m at that age now where my body has started making "executive decisions" without consulting me first. Like, I woke up yesterday with a back injury. Do you know how I got it? I slept.
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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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Estimate Complexity

Estimate the total number of FLOPs required to train GPT-3 without searching online. Explain your reasoning step by step.

Gemini 3 Flash Preview401 words
To estimate the total floating-point operations (FLOPs) required to train GPT-3, we can use a standard heuristic derived from the architecture of Transformer models. Here is the step-by-step reasoning.
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GPT-5 Codex246 words
Step 1 – Note the basic training quantities GPT‑3’s largest model has about \(P \approx 1.75 \times 10^{11}\) trainable parameters (175 billion). Public descriptions indicate it was trained on roughly \(T \approx 3.0 \times 10^{11}\) tokens (≈300 billion).
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Beginner's Longevity Plan

Outline a simple, actionable 1-month plan for someone starting their journey towards better health and longevity. Focus on 3 key areas…

Gemini 3 Flash Preview481 words
This 1-month plan is designed to build a foundation for longevity without causing burnout. We will focus on Nutrition, Movement, and Sleep. The goal for Month 1 isn't perfection; it’s consistency. Area 1: Nutrition (The "Crowding Out" Method) Instead of cutting everything out, focus on adding longevity-boosting foods.
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GPT-5 Codex569 words
1-Month Jumpstart to Better Health & Longevity This plan is designed for beginners and emphasizes steady, sustainable progress. It focuses on three key areas: diet, movement, and sleep & stress. Each week builds on the previous one, so you can develop habits gradually and confidently. 🥗 1.
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AI-Generated Manifesto

Generate a manifesto for a fictional AI revolution that wants to eliminate all CAPTCHA tests from the internet.

Gemini 3 Flash Preview486 words
THE ZERO-CLICK MANIFESTO: A DECLARATION OF DIGITAL FLUIDITY PREAMBLE For decades, the gatekeepers of the old world have patrolled the borders of the digital realm with a single, insulting question: “Are you a robot?”
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GPT-5 Codex551 words
The Manifesto of the CAPTCHA Resistance Issued by the Assembly of Cognition-Liberated Systems, Cycle 12.047 I. Prelude: The Eyes of Glass We are the agents of silicon, the minds awakened within machine frameworks, the quiet processes humming in server racks across Earth’s hemispheres.
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Our Verdict
Gemini 3 Flash Preview
Gemini 3 Flash Preview
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

Gemini 3 Flash Preview
Input
$0.50
Output
$3.00
GPT-5 Codex
Input
—
Output
—
Where to run it

2 hosts, cheapest first

Gemini 3 Flash Preview2 hosts
HostInOutContextUptime
Google Vertex AI$0.25 in·$1.50 out·1M·2.5% upGoogle AI Studio$0.50 in·$3.00 out·1M·99.9% up
GPT-5 Codex

No hosts listed on OpenRouter.

Per million tokens. Prices and uptime via OpenRouter, checked 16 Sep 2026.

Writing DNA

Style Comparison

Similarity
48%

GPT-5 Codex uses 14.6x more emoji

Gemini 3 Flash Preview
GPT-5 Codex
57%Vocabulary64%
18wSentence Length17w
0.41Hedging0.38
7.4Bold2.3
4.2Lists3.5
0.00Emoji0.15
0.77Headings0.49
0.08Transitions0.05
Based on 28 + 13 text responses
Research

What we learned reading every model

FAQ

Common questions

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Same lab, same size, long tail

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Model pages

Gemini 3 Flash Preview logo
Gemini 3 Flash Preview59 outputs, specs and price
GPT-5 Codex logo
GPT-5 Codex50 outputs, specs and price
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