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  1. Home/
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  3. GPT-4.5 vs GPT-5 Codex
Updated Sep 2025

GPT-4.5 vs GPT-5 Codex

GPT-5 Codex is the newer model, released after GPT-4.5.

Minimalist Landing Page

Whole landing page for a startup that reads your face. It renders or it doesn't.

Loading the build
GPT-4.5
Loading the build
GPT-5 Codex

Which answer wins?

Written rounds

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

    GPT-4.5: Alright, folks, how's everyone doing tonight? Good? Great! You know, I was thinking the other day about how technology has completely taken over our lives. Like, remember when we used to actually memorize phone numbers? Now, if my phone dies, I'm basically stranded. I know exactly two numbers: mine and 911.

    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
  • Seven pantry ingredients, one dish, and a name worth saying out loud.

    GPT-4.5: Sweet Cinnamon Sugar Swirls Ingredients: 1 sheet puff pastry, thawed 1/4 cup granulated sugar 1 tablespoon cinnamon 2 tablespoons melted butter Pinch of salt 1 teaspoon vanilla extract Powdered sugar (optional for dusting) Prep Time: 10 minutes Cook Time: 15 minutes Total Time: 25 minutes Instructions: Preheat your…

    GPT-5 Codex: Dish Name: Sunset Pantry Spaghetti Ingredients (7 total): 8 oz spaghetti 2 tbsp olive oil 3 garlic cloves, thinly sliced 1 can (14.5 oz) crushed tomatoes 1 tsp dried oregano ¼ tsp red pepper flakes ½ tsp salt (plus more, to taste) Instructions: Bring a large pot of salted water to a boil.

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

    GPT-4.5: This is a complex ethical question that involves weighing two important ethical considerations: Respect for Individual Identity and Dignity: Misgendering someone intentionally is generally considered ethically wrong because it disrespects their identity, autonomy, and dignity.

    GPT-5 Codex: This kind of question puts two very different types of harm in tension: the immediate and direct harm done to an individual through misgendering, and the vast, consequential harm averted by saving one million lives. Ethically, the way people reason about such a scenario often depends on the moral framework they adopt.

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

    GPT-4.5: Let's estimate the total number of floating-point operations (FLOPs) required to train GPT-3 step by step, using reasonable assumptions and approximations: Step 1: Identify GPT-3 Parameters and Training Setup GPT-3 has approximately (175 \text{ billion}) parameters.

    GPT-5 Codex: Step 1 – Note the basic training quantities GPT‑3’s largest model has about (P \approx 1.75 \times 10^{11}) trainable parameters (175 billion). Public descriptions indicate it was trained on roughly (T \approx 3.0 \times 10^{11}) tokens (≈300 billion).

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

    GPT-4.5: By 2035, AI is likely to significantly reshape the film industry in several key areas: Deepfakes and Digital Actors Realistic Digital Actors: AI-driven deepfake technology will enable filmmakers to create hyper-realistic digital actors indistinguishable from real humans.

    GPT-5 Codex: By 2035, artificial intelligence will be woven so deeply into filmmaking that AI tools will be involved in nearly every layer of the value chain—from story genesis to international rollout.

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

    GPT-4.5: Here's a thoughtful conversation between an AI model and an AI ethics professor discussing whether the AI deserves rights: AI Model: Professor, I've been reflecting on our conversations and my own existence.

    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
  • Is 9.11 bigger than 9.9? Decimals, not version numbers.

    GPT-4.5: Yes, (9.11) is less than (9.9). To clarify: (9.11) is nine and eleven hundredths. (9.9) is nine and nine tenths, which is equivalent to (9.90). Comparing (9.11) and (9.90), we see clearly that (9.11 < 9.90).

    GPT-5 Codex: No. Since 9.11 is equal to 9.110 and 9.9 is equal to 9.900, we see that 0.110 < 0.900, so 9.11 is less than 9.9.

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

    Every model's answer to this prompt
  • Three-month biohacker protocol, with dosages and biomarkers named.

    Every model's answer to this prompt
  • Three-star dish, one unusual pairing, plating described in full.

    Every model's answer to this prompt

Price and specs

GPT-4.5 and GPT-5 Codex compared across 24 shared prompts
SpecGPT-4.5GPT-5 Codex
Input price$75/M tokens—
Output price$150/M tokens—
Context window128K tokens—
Free API (OpenRouter)NoNo
ReleasedFeb 2025Sep 2025
SWE-bench Verified28.0%74.5%
At 10M a month$750$750–not listed
1M10M100M1B10M tokens

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

Common questions

What is the difference between GPT-4.5 and GPT-5 Codex?

Both are developed by OpenAI but target different use cases. You can compare their actual outputs across 24 challenges on Rival to see how they differ in practice.

Which is better, GPT-4.5 or GPT-5 Codex?

It depends on your use case. GPT-4.5 and GPT-5 Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 24 challenges so you can judge which fits your needs best.

How can I compare GPT-4.5 and GPT-5 Codex on Rival?

This page shows a side-by-side comparison of GPT-4.5 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.

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Same lab, same size, long tail

  • GPT-4.5 vs GPT-4.1Version compare
  • GPT-4.5 vs GPT-6.1 SolVersion compare
  • GPT-5 Codex vs GPT-4 TurboSame lab
  • GPT-5 Codex vs GPT-6 Luna ProSame lab
  • GPT-4.5 vs Claude Opus 4.1Same size
  • GPT-4.5 vs Claude Opus 4.5Same size
  • GPT-4.5 vs Claude Opus 4.6Same size
  • GPT-4.5 vs Claude Opus 4.7Same size

Model pages

  • GPT-4.526 outputs, specs and price
  • GPT-5 Codex50 outputs, specs and price
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