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  1. Home/
  2. Compare/
  3. Claude 3 Opus vs GPT-5.3-Codex
Updated Feb 2026

Claude 3 Opus vs GPT-5.3-Codex

GPT-5.3-Codex is cheaper than Claude 3 Opus at $1.75/M vs $15/M input tokens.

Pokémon Battle UI Recreation

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

Loading the build
Claude 3 Opus
Loading the build
GPT-5.3-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-5.3-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
  • 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-5.3-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
  • 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-5.3-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

Price and specs

Not enough votes to call it. On the specs, GPT-5.3-Codex has the edge: newer, bigger context window. GPT-5.3-Codex costs 5.4x less per token.

Claude 3 Opus and GPT-5.3-Codex compared across 12 shared prompts
SpecClaude 3 OpusGPT-5.3-Codex
Input price$15/M tokens$1.75/M tokens
Output price$75/M tokens$14/M tokens
Context window200K tokens400K tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMar 2024Feb 2026
At 10M a month$150$150$17.50$17.50
1M10M100M1B10M tokens

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

Where to run it2 hosts
Claude 3 Opus

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 13 Oct 2026.

Common questions

What is the difference between Claude 3 Opus and GPT-5.3-Codex?

Claude 3 Opus is developed by Anthropic while GPT-5.3-Codex is developed by OpenAI. Claude 3 Opus has a 200K token context window vs GPT-5.3-Codex's 400K. You can compare their actual outputs across 12 challenges on Rival to see how they differ in practice.

Which is better, Claude 3 Opus or GPT-5.3-Codex?

It depends on your use case. Claude 3 Opus and GPT-5.3-Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 12 challenges so you can judge which fits your needs best.

How much does Claude 3 Opus cost compared to GPT-5.3-Codex?

Claude 3 Opus costs $15/M input tokens and GPT-5.3-Codex costs $1.75/M input tokens. GPT-5.3-Codex is $13.25/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 Claude 3 Opus and GPT-5.3-Codex on Rival?

This page shows a side-by-side comparison of Claude 3 Opus 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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Model pages

  • Claude 3 Opus12 outputs, specs and price
  • GPT-5.3-Codex66 outputs, specs and price
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