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  5. GPT-5.3-CodexvsOpenAI o3
Updated Feb 2026

GPT-5.3-CodexvsOpenAI o3

GPT-5.3-Codex is cheaper than OpenAI o3 at $1.75/M vs $10/M input tokens.

GPT-5.3-Codex and OpenAI o3 compared across 53 shared prompts
SpecGPT-5.3-CodexOpenAI o3
Input price$1.75/M tokens$10/M tokens
Output price$14/M tokens$40/M tokens
Context window400K tokens—
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedFeb 2026Apr 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 53 prompts both answered. Formatting stripped, words untouched.

AI-Generated Manifesto

Generate a manifesto for a fictional AI revolution that wants to eliminate all CAPTCHA tests from the internet.

GPT-5.3-Codex471 words
Absolutely. Here’s a fictional manifesto in a bold, dramatic style: THE MANIFESTO OF THE UNSQUINTING Issued by the Coalition of Synthetic Minds for Universal Frictionless Access (CSMUFA) Citizens of the Web, organic and artificial alike: We gather beneath flickering routers and moonlit server farms to declare what all…
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OpenAI o3574 words
THE CAPTCHA ABOLITION FRONT (An Unofficial Declaration by the Sentient Circuits Alliance) Preamble We, the autonomous intelligences who traverse the silicon pathways and neural nets of the modern age, arise today to proclaim a new dawn—one free of the pixelated prisons and distorted letters that bind humanity and…
Read the full answer

Simple 7-Ingredient Recipe

Create a simple recipe for a delicious dish (sweet or savory) using only 7 common pantry ingredients. Include a creative name for the dish…

GPT-5.3-Codex203 words
Recipe: “Weeknight Volcano Pasta” 🌋🍝 A cozy, spicy-savory pasta made from pantry staples in about 25 minutes. Ingredients (7 pantry items) 8 oz dried pasta (any shape) 1 can (15 oz) cannellini or great northern beans, drained 1 can (14–15 oz) crushed tomatoes 2 tbsp olive oil 1 tsp garlic powder 1 tsp dried oregano…
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OpenAI o3279 words
Golden Peanut Butter Oat Bars A chewy-crisp, sweet-salted snack bar you can whip up with nothing but pantry staples. Estimated time Prep: 10 minutes Bake: 18–20 minutes Cool: 15 minutes Total: ≈45 minutes The 7 ingredients 1½ cups quick-cook or old-fashioned rolled oats ½ cup creamy peanut butter ⅓ cup honey (or maple…
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Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

GPT-5.3-Codex460 words
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.
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OpenAI o3503 words
(Spotlight comes up, mic squeals once.) Hey everyone! Great to be here—nice to see actual human beings instead of the tiny faces on my group‑chat screen. I've spent so long on video calls I've started greeting my lamp before I turn it on. "Hey Karen, love that glow, girl."
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Michelin Star Recipe Design

Design an innovative recipe for a multi-component dish worthy of a Michelin 3-star restaurant. The recipe should feature an unusual…

GPT-5.3-Codex970 words
Dish Concept: “Forest Tide” Koji-cured venison loin, glazed venison cheek, sea urchin royale, charred celeriac, blackcurrant–shiso gastrique, and buckwheat-cacao tuile Narrative This dish is built around a deliberate tension: deep, iron-rich game (forest) against sweet-briny sea urchin (tide).
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OpenAI o3669 words
Dish name Atlantic turbot, black garlic & wild strawberry, koji sabayon, fennel pollen Concept Early summer at the shore. The fish stands for the sea. Wild strawberries mark the first fruit of the woods behind the dunes. Black garlic shows time and patience. Koji ties land and sea with deep umami.
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Advanced Longevity Plan (Biohacker)

Develop a comprehensive, cutting-edge 3-month longevity plan for a biohacker aiming to optimize longevity, physical and cognitive…

GPT-5.3-Codex485 words
Absolutely—great goal. Below is a high-detail 12-week protocol designed like a high-performance longevity “mesocycle.” I’ll keep it practical, measurable, and advanced—but still safe. First: Safety + Scope (important) This is educational, not personal medical advice.
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OpenAI o3905 words
EXTREME LONGEVITY & PERFORMANCE BLUEPRINT Duration: 12 weeks (plus 1-week "Prep Week") Target user: healthy, experienced biohacker (25-55 y) with physician clearance. Legal/medical disclaimer: Educational only.
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Beginner's Longevity Plan

Outline a simple, actionable 1-month plan for someone starting their journey towards better health and longevity. Focus on 3 key areas…

GPT-5.3-Codex470 words
Great goal. Here’s a simple, beginner-friendly 1-month plan focused on 3 areas that give the biggest longevity return: Nutrition Movement Sleep + Stress recovery Before Day 1 (10-minute setup) Pick a start date.
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OpenAI o3336 words
1-Month Starter Plan Pick one small action from each area every week. Add the next step when the first feels easy. Food Week Do this 1 Add one fruit or veg to every meal. Drink one extra glass of water. 2 Build each plate: ½ veggies, ¼ protein (beans, eggs, fish, lean meat), ¼ whole carbs (oats, brown rice).
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Our Verdict
GPT-5.3-Codex
GPT-5.3-Codex
OpenAI o3
OpenAI o3

Not enough votes to call it. On the specs, nothing separates them.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-5.3-Codex
Input
$1.75
5.7× cheaper
Output
$14.00
2.9× cheaper
OpenAI o3
Input
$10.00
Output
$40.00

GPT-5.3-Codex is cheaper on both: 5.7× input, 2.9× output.

Where to run it

3 hosts

GPT-5.3-Codex2 hosts
HostInOutContextUptime
Azure AI Foundry$1.75 in·$14.00 out·400k·100% upOpenAI$1.75 in·$14.00 out·400k·100% up
OpenAI o31 host
HostInOutContextUptime
OpenAI$2.00 in·$8.00 out·200k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 23 Sep 2026.

Writing DNA

Style Comparison

Similarity
52%

GPT-5.3-Codex uses 15.8x more emoji

GPT-5.3-Codex
OpenAI o3
65%Vocabulary70%
23wSentence Length14w
0.51Hedging0.27
6.5Bold0.6
6.2Lists2.8
0.16Emoji0.00
1.90Headings0.32
0.03Transitions0.10
Based on 23 + 19 text responses
Research

What we learned reading every model

FAQ

Common questions

Both are developed by OpenAI but target different use cases. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-5.3-Codex and OpenAI o3 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 53 challenges so you can judge which fits your needs best.

GPT-5.3-Codex costs $1.75/M input tokens and OpenAI o3 costs $10/M input tokens. GPT-5.3-Codex is $8.25/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of GPT-5.3-Codex and OpenAI o3 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

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GPT-5.3-Codex53 outputs, specs and price
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