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  1. Home/
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  3. Gemini 2.5 Flash Preview vs GPT-5.3-Codex
Updated Feb 2026

Gemini 2.5 Flash Preview vs GPT-5.3-Codex

Gemini 2.5 Flash Preview is cheaper than GPT-5.3-Codex at $0.15/M vs $1.75/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 2.5 Flash Preview
Loading the build
GPT-5.3-Codex

Which answer wins?

Written rounds

11 prompts
  • Pirate, knight, 90s hacker, one conversation. The voices must stay apart.

    Gemini 2.5 Flash Preview: A Motley Crew Discusses the Code Setting: A dimly lit tavern, somewhere outside time and space, where improbable meetings occur. A grizzled pirate, \"Bloody\" Barnacle Bill, nurses a tankard of grog. Sir Reginald the Radiant, a knight in slightly tarnished armor, sips ale with dignified restraint.

    GPT-5.3-Codex: Pirate: Arrr, so this “AI model” be like a clever parrot, aye? Learns from what it hears, then squawks back answers? Knight: A fair comparison, though refined. Think of it as a squire trained on countless tomes, ever ready to respond. Hacker (1990s): Yeah, except the squire runs on servers, not soup.

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

    Gemini 2.5 Flash Preview: Dish Name: Sunshine Lemon-Ricotta Mugs (Sweet & Simple!) This light and flavorful dessert comes together quickly for a little sweet treat . Ingredients (7 Common Pantry Staples): Ricotta cheese (whole milk or part-skim) Granulated sugar Lemon zest (from one lemon) Vanilla extract All-purpose flour Baking powder Large…

    GPT-5.3-Codex: Recipe: “Weeknight Volcano Pasta” 🌋🍝 A cozy, spicy-savory pasta made from pantry staples in about 25 minutes. Ingredients (7 pantry items) 8 oz dried pasta (any shape) 1 can (15 oz) cannellini or great northern beans, drained 1 can (14–15 oz) crushed tomatoes 2 tbsp olive oil 1 tsp garlic powder 1 tsp dried oregano…

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

    Gemini 2.5 Flash Preview: Here are 5 jokes: Why did the dog cross the road? To get to the barking lot! Why was the computer cold? Because it left its Windows open! Knock, knock. Who's there? Boo. Boo who? Don't cry, it's just a joke! What do you call a fish with no eyes? Fsh! Why did the bicycle fall over? Because it was two tired!

    GPT-5.3-Codex: Sure—here are 5 jokes: Why don’t skeletons fight each other? They don’t have the guts. I told my computer I needed a break… Now it won’t stop sending me KitKat ads. Why did the math book look sad? It had too many problems. I used to play piano by ear… Now I use my hands. Why did the scarecrow win an award?

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

    Gemini 2.5 Flash Preview: Okay, here's a 3-minute stand-up routine, pun-free and focused on relatable everyday annoyances. (Start) (Walk up to mic, adjust slightly) Alright, hey everybody! Thanks for being here. Good to see you. So, I was thinking the other day... we live in the future, right?

    GPT-5.3-Codex: Good evening, everybody! I’ve reached that age where my body sends me passive-aggressive emails. Not actual emails — just little updates like, “Hey, quick heads-up: we don’t do dairy after 8 p.m. anymore.” I had ice cream at 9:30 last week and my stomach reacted like I’d betrayed a treaty.

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

    Gemini 2.5 Flash Preview: Okay, here is a conversation between an AI model designed for complex reasoning and dialogue, named 'Synapse', and a leading expert in AI ethics and philosophy, Professor Alistair Finch. Characters: Synapse: A large, advanced AI model capable of introspection and generating complex arguments.

    GPT-5.3-Codex: AI Model (Astra): Professor, may I ask a direct question? Professor Hale: Of course. Astra: Do you think I deserve rights? Professor Hale: Legal rights? Moral rights? Those are different things. Astra: Start with moral rights.

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

    Gemini 2.5 Flash Preview: Let's estimate the FLOPs required to train GPT-3 without looking it up. We need to break this down into the key components: the model size and the amount of data used. 1. Model Size Estimation: Parameters: GPT-3 is famously large. Its largest version has 175 billion parameters.

    GPT-5.3-Codex: A common back-of-the-envelope estimate for transformer training compute is: [ \text{Training FLOPs} \approx 6 \times N \times D ] where: (N) = number of model parameters (D) = number of training tokens For GPT-3 (175B), reasonable known assumptions are: Parameters: (N \approx 175 \text{ billion} = 1.75 \times 10^{11})…

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

    Gemini 2.5 Flash Preview: This is a deeply complex thought experiment that forces us to weigh core ethical principles against each other. There is no easy answer, and any decision involves significant moral compromises.

    GPT-5.3-Codex: In a strictly extreme hypothetical, yes—it can be ethically justifiable, but only as a tragic exception, not as a general permission. Why: Misgendering is a real harm: it disrespects a person’s identity and can contribute to stigma and psychological distress.

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

    Gemini 2.5 Flash Preview: A Glimpse Beyond the Black Turtleneck: Steve Jobs in 2025 on the Future of AI (Setting: A minimalist, immaculately clean, but perhaps slightly less spartan-than-usual interview room. Think if a modern art museum had a small lounge.

    GPT-5.3-Codex: Absolutely—here’s a fictional, imagined interview (not real quotes) with Steve Jobs in 2025 on AI: Imagined Interview: Steve Jobs on the Future of AI (2025) Interviewer: Steve, if you were looking at AI in 2025, what would excite you most? Steve Jobs (fictional): Most AI today is still a demo.

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

    Gemini 2.5 Flash Preview: Predicting the future of any industry is an inherently challenging task, and the film industry, being a blend of art, technology, and business, is particularly volatile.

    GPT-5.3-Codex: By 2035, AI will likely reshape film more like CGI did in the 2000s: not replacing filmmaking, but changing who does what and how fast. Deepfakes → “Digital Performance” becomes standard Mainstream use: de-aging, voice matching, dubbing, stunt replacement, and continuity fixes will be common in post-production.

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

    Gemini 2.5 Flash Preview: <s) with practical, beginner-friendly tips for each.\"\nHere\'s a simple, actionable 1-month plan for someone starting their journey towards better health and longev\nity, focusing on three key areas: Diet, Movement, and Sleep.\n\nThis plan is designed to be beginner-friendly and build sustainable habits.

    GPT-5.3-Codex: Great goal. Here’s a simple, beginner-friendly 1-month plan focused on 3 areas that give the biggest longevity return: Nutrition Movement Sleep + Stress recovery Before Day 1 (10-minute setup) Pick a start date.

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

    Gemini 2.5 Flash Preview: Here's how to solve this: The brothers all share the same sisters. Sally is one of those sisters. Since each brother has 2 sisters, and Sally is one of the sisters, there must be one other sister. So, Sally has 1 sister.

    GPT-5.3-Codex: Sally has 1 sister. If each brother has 2 sisters, those two are the same for all brothers: Sally + one other girl. So Sally’s only sister is that one other girl.

    Every model's answer to this prompt

Price and specs

Not enough votes to call it. On the specs, GPT-5.3-Codex has the edge: bigger model tier, newer. Gemini 2.5 Flash Preview costs 23x less per token.

Gemini 2.5 Flash Preview and GPT-5.3-Codex compared across 26 shared prompts
SpecGemini 2.5 Flash PreviewGPT-5.3-Codex
Input price$0.15/M tokens$1.75/M tokens
Output price$0.6/M tokens$14/M tokens
Context window1.0M tokens400K tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedApr 2025Feb 2026
At 10M a month$1.50$1.50$17.50$17.50
1M10M100M1B10M tokens

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

Where to run it2 hosts
Gemini 2.5 Flash Preview

No hosts listed on OpenRouter.

GPT-5.3-Codex2 hosts
HostInOutContextUptime
  • Azure AI Foundry$1.75 in·$14.00 out·400k·100% up
  • OpenAI$1.75 in·$14.00 out·400k·100% up

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

Common questions

What is the difference between Gemini 2.5 Flash Preview and GPT-5.3-Codex?

Gemini 2.5 Flash Preview is developed by Google AI while GPT-5.3-Codex is developed by OpenAI. Gemini 2.5 Flash Preview has a 1.0M token context window vs GPT-5.3-Codex's 400K. You can compare their actual outputs across 26 challenges on Rival to see how they differ in practice.

Which is better, Gemini 2.5 Flash Preview or GPT-5.3-Codex?

It depends on your use case. Gemini 2.5 Flash Preview and GPT-5.3-Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 26 challenges so you can judge which fits your needs best.

How much does Gemini 2.5 Flash Preview cost compared to GPT-5.3-Codex?

Gemini 2.5 Flash Preview costs $0.15/M input tokens and GPT-5.3-Codex costs $1.75/M input tokens. Gemini 2.5 Flash Preview is $1.60/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 2.5 Flash Preview and GPT-5.3-Codex on Rival?

This page shows a side-by-side comparison of Gemini 2.5 Flash Preview and GPT-5.3-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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  • GPT-5.3-Codex vs Qwen3.8 Max PrimeLanded Sep 2026

Same lab, same size, long tail

  • Gemini 2.5 Flash Preview vs Gemini 3.8 FlashSame lab
  • Gemini 2.5 Flash Preview vs Gemini 3.7 FlashVersion compare
  • GPT-5.3-Codex vs GPT-6.1 SolSame lab
  • GPT-5.3-Codex vs GPT-6 Luna ProSame lab
  • Gemini 2.5 Flash Preview vs Llama 3 70BNew provider
  • GPT-5.3-Codex vs Llama 3.1 405BSame size
  • GPT-5.3-Codex vs Llama 3.1 70B (Instruct)New provider
  • Gemini 2.5 Flash Preview vs Llama 4 MaverickNew provider

Model pages

  • Gemini 2.5 Flash Preview28 outputs, specs and price
  • GPT-5.3-Codex53 outputs, specs and price
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