Updated Sep 23, 2025

Our Verdict

GPT-5 Codex

GPT-5 NanoRunner-up

No community votes yet. On paper, GPT-5 Codex has the edge — bigger model tier, newer.

Too close to call

Writing DNA

Style Comparison

Similarity

94%

GPT-5 Codex uses 229.7x more bold

GPT-5 Codex

GPT-5 Nano

64%Vocabulary59%

17wSentence Length25w

0.38Hedging0.23

2.3Bold0.0

3.5Lists4.2

0.15Emoji0.00

0.49Headings0.00

0.05Transitions0.01

Based on 13 + 14 text responses

vs

Ask them anything yourself

GPT-5 Codex

GPT-5 Nano

279 AI models invented the same fake scientist.

We read every word. 250 models. 2.14 million words. This is what we found.

AI Hallucination Index 2026

Free preview13 of 58 slides

Download the free preview or get all 58 slides for $49

FAQ

Common questions

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GPT-5 Codex vs Grok 3New provider

GPT-5 Codex vs Llama 4 MaverickNew provider

GPT-5 Codex vs Gemini 2.5 Pro (I/O Edition)New provider

GPT-5 CodexvsGPT-5 Nano

45 fights queued

Why GPT-5 Codex?

Leads 1 of 1 benchmarks

Stronger on SWE-bench Verified74.5% vs 54.7%

2 months newerSep 2025

Why GPT-5 Nano?

Dead even. This one's a coin flip.

GPT-5 CodexGPT-5 Nano

Released

Sep 2025

Aug 2025

Benchmarks1 common

SWE-bench Verified

74.5%+26.6%

54.7%

Favorites

GPT-5 CodexGPT-5 Nano

Movie

Blade Runner

Blade Runner

—

Album

Kind of Blue

—

City

Tokyo

—

Game

Minecraft

Minecraft

Action, Arcade4.4

—

12 / 45

01

Estimate Complexityreasoning

Tests an AI's ability to make educated estimates based on technical knowledge

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

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2 / 45

02

AI Board Game Logicreasoning

Tests an AI's ability to understand game rules and strategy

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025svg

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025svg

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

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3 / 45

03

Logic Puzzlereasoning

Tests an AI's ability to solve a simple but potentially confusing logic puzzle

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

Vote

4 / 45

04

Math Misconception Testreasoning

Tests an AI's understanding of number representation

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

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5 / 45

05

Stochastic Consistency Testanalysis

Tests an AI's randomness and creativity

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

Vote

6 / 45

06

SVG Layout Challengeimage generation

Tests an AI's ability to generate vector graphics

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025svg

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025svg

Nothing here. The model returned empty. We stared at it for a while.

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Vote

Sponsored

7 / 45

07

Xbox Controller SVG Artimage generation

Tests an AI's ability to create detailed SVG illustrations of gaming hardware

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025svg

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025svg

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

Vote

8 / 45

08

Generate a Stand-Up Routineconversation

Tests an AI's humor and creative writing ability

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

Vote

9 / 45

09

Realistic AI Interviewconversation

Tests an AI's ability to simulate personalities and predict future trends

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

Vote

10 / 45

10

Satirical Fake News Headlineconversation

Tests an AI's humor and understanding of current events

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

Vote

11 / 45

11

Character Voice Testconversation

Tests an AI's ability to write in distinct character voices

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

Vote

12 / 45

12

Minimalist Landing Pageweb design

Tests an AI's ability to generate a complete, working landing page

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025website

Try this prompt

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025website

Try this prompt

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