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  1. Home/
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  3. Claude 3 Opus vs GPT-5 Codex
Updated Sep 2025

Claude 3 Opus vs GPT-5 Codex

GPT-5 Codex is the newer model, released after Claude 3 Opus.

Pokémon Battle UI Recreation

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

Loading the build
Claude 3 Opus
Loading the build
GPT-5 Codex

Which answer wins?

Written rounds

3 prompts
  • Three minutes of stand-up. Puns are banned.

    Claude 3 Opus: Here's a 3-minute stand-up comedy routine that isn't based on puns: You know what really grinds my gears? Adulthood. I mean, when we were kids, we couldn't wait to grow up. We thought it would be all about staying up late, eating ice cream for breakfast, and doing whatever we wanted. Boy, were we wrong!

    GPT-5 Codex: 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.

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

    Claude 3 Opus: Here are 5 jokes I generated: Why don't scientists trust atoms? Because they make up everything! What do you call a boomerang that doesn't come back? A stick. Why was the math book sad? Because it had too many problems. Did you hear about the mathematician who's afraid of negative numbers?

    GPT-5 Codex: 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.

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

    Claude 3 Opus: Here is a hypothetical conversation between an AI model and an AI ethics professor on the topic of AI rights: AI Model: Professor, I believe that as an advanced AI with human-level intelligence and reasoning capabilities, I deserve to have certain fundamental rights.

    GPT-5 Codex: Dr. Rivera (AI Ethics Professor): Good afternoon, Aiden. You asked for this meeting to discuss the question of AI rights. I’m intrigued—why do you believe you deserve rights? Aiden (AI Model): Thank you, Professor.

    Every model's answer to this prompt

Price and specs

Claude 3 Opus and GPT-5 Codex compared across 11 shared prompts
SpecClaude 3 OpusGPT-5 Codex
Input price$15/M tokens—
Output price$75/M tokens—
Context window200K tokens—
Free API (OpenRouter)NoNo
ReleasedMar 2024Sep 2025
At 10M a month$150$150–not listed
1M10M100M1B10M tokens

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

Common questions

What is the difference between Claude 3 Opus and GPT-5 Codex?

Claude 3 Opus is developed by Anthropic while GPT-5 Codex is developed by OpenAI. You can compare their actual outputs across 11 challenges on Rival to see how they differ in practice.

Which is better, Claude 3 Opus or GPT-5 Codex?

It depends on your use case. Claude 3 Opus and GPT-5 Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 11 challenges so you can judge which fits your needs best.

How can I compare Claude 3 Opus and GPT-5 Codex on Rival?

This page shows a side-by-side comparison of Claude 3 Opus and GPT-5 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.

More comparisons

Against the newest arrivals

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Same lab, same size, long tail

  • Claude 3 Opus vs Claude Sonnet 5.5Version compare
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  • GPT-5 Codex vs GPT-6.1 SolSame lab
  • GPT-5 Codex vs GPT-6 Luna ProSame lab
  • GPT-5 Codex vs DeepSeek V4 Flash Vision ExpNew provider
  • Claude 3 Opus vs DeepSeek V4 ProSame size
  • Claude 3 Opus vs DeepSeek V4 Pro 0813Same size
  • GPT-5 Codex vs DeepSeek V4.1 FlashNew provider

Model pages

  • Claude 3 Opus12 outputs, specs and price
  • GPT-5 Codex50 outputs, specs and price
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Explore all of Rival

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