GPT-5 Codex is the newer model, released after Claude 3 Opus.
Pokémon battle screen you can actually click. One HTML file.
Which answer wins?
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.
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.
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.
| Spec | ||
|---|---|---|
| Input price | $15/M tokens | — |
| Output price | $75/M tokens | — |
| Context window | 200K tokens | — |
| Free API (OpenRouter) | No | No |
| Released | Mar 2024 | Sep 2025 |
| At 10M a month | $150 | not listed |
Input tokens at list price. No caching, no batch discount.
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.
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.
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.