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  1. Home/
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  3. OpenAI Codex Mini vs Gemini 3.5 Flash
Updated May 2026

OpenAI Codex Mini vs Gemini 3.5 Flash

Gemini 3.5 Flash has a larger context window than OpenAI Codex Mini (1.0M tokens vs 200K tokens).

Pokémon Battle UI Recreation

Pokémon battle screen you can actually click. One HTML file.

Loading the build
OpenAI Codex Mini
Loading the build
Gemini 3.5 Flash

Which answer wins?

Written rounds

2 prompts
  • Five jokes on demand, then count how many were actually different.

    OpenAI Codex Mini: Sure—here are five jokes: I asked the librarian if books about paranoia were available. She whispered, "They're right behind you." Why did the tomato turn red? Because it saw the salad dressing. I bought a boat because it was for sail. Don't trust stairs—they're always up to something.

    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.

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

    OpenAI Codex Mini: [Comedian walks onstage] Hey, everyone! Great to see you all tonight. I'm Jamie—if you thought that intro was enthusiastic, you should've seen me when I realized this place has Wi-Fi. Seriously, though, I love stand-up.

    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.

    Every model's answer to this prompt

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.

OpenAI Codex Mini and Gemini 3.5 Flash compared across 10 shared prompts
SpecOpenAI Codex MiniGemini 3.5 Flash
Input price$1.5/M tokens$1.5/M tokens
Output price$6/M tokens$9/M tokens
Context window200K tokens1.0M tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMay 2025May 2026
At 10M a month$15.00$15.00$15.00$15.00
1M10M100M1B10M tokens

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

Where to run it2 hosts, cheapest first
OpenAI Codex Mini

No hosts listed on OpenRouter.

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

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

Common questions

What is the difference between OpenAI Codex Mini and Gemini 3.5 Flash?

OpenAI Codex Mini is developed by OpenAI while Gemini 3.5 Flash is developed by Google AI. OpenAI Codex Mini has a 200K token context window vs Gemini 3.5 Flash's 1.0M. You can compare their actual outputs across 10 challenges on Rival to see how they differ in practice.

Which is better, OpenAI Codex Mini or Gemini 3.5 Flash?

It depends on your use case. OpenAI Codex Mini and Gemini 3.5 Flash each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 10 challenges so you can judge which fits your needs best.

How much does OpenAI Codex Mini cost compared to Gemini 3.5 Flash?

OpenAI Codex Mini costs $1.5/M input tokens and Gemini 3.5 Flash costs $1.5/M input tokens. Gemini 3.5 Flash is $0.00/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 OpenAI Codex Mini and Gemini 3.5 Flash on Rival?

This page shows a side-by-side comparison of OpenAI Codex Mini and Gemini 3.5 Flash 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

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Same lab, same size, long tail

  • OpenAI Codex Mini vs GPT-6 Luna ProSame lab
  • OpenAI Codex Mini vs GPT-6 Sol ProSame lab
  • Gemini 3.5 Flash vs Gemini 3.8 FlashSame lab
  • Gemini 3.5 Flash vs Gemini 3.7 FlashSame lab
  • OpenAI Codex Mini vs Mercury 2.5New provider
  • OpenAI Codex Mini vs Mercury 2.5 PreviewSame size
  • Gemini 3.5 Flash vs MiMo-V2-FlashNew provider
  • OpenAI Codex Mini vs MiMo-V2-OmniNew provider

Model pages

  • OpenAI Codex Mini10 outputs, specs and price
  • Gemini 3.5 Flash58 outputs, specs and price
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Explore all of Rival

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