Updated Sep 23, 2025

Our Verdict

GPT-5 Codex

OpenAI o4-miniRunner-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

98%

GPT-5 Codex uses 229.7x more bold

GPT-5 Codex

OpenAI o4-mini

64%Vocabulary73%

17wSentence Length15w

0.38Hedging0.18

2.3Bold0.0

3.5Lists2.1

0.15Emoji0.00

0.49Headings0.00

0.05Transitions0.02

Based on 13 + 10 text responses

vs

Ask them anything yourself

GPT-5 Codex

OpenAI o4-mini

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 CodexvsOpenAI o4-mini

34 fights queued

Why GPT-5 Codex?

Leads 1 of 1 benchmarks

Stronger on SWE-bench Verified74.5% vs 68.1%

5 months newerSep 2025

Why OpenAI o4-mini?

Dead even. This one's a coin flip.

GPT-5 CodexOpenAI o4-mini

Input price

—

$1.10/M

Output price

—

$4.40/M

Released

Sep 2025

Apr 2025

Benchmarks1 common

SWE-bench Verified

74.5%+8.6%

68.1%

Favorites

GPT-5 CodexOpenAI o4-mini

Movie

Blade Runner

Blade Runner

The Shawshank Redemption

The Shawshank Redemption

Album

Kind of Blue

—

City

Tokyo

—

Game

Minecraft

Minecraft

Action, Arcade4.4

—

12 / 34

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025text

Here's a back‐of‐the‐envelope derivation that gets us into the right ballpark (∼10²³ FLOPs total):

Model size
• GPT–3 "175 B" has about P ≃1.75×10¹¹ parameters.
Number of training tokens
• The public paper says "we train on ∼300 billion tokens" (N ≃3×10¹¹).
FLOPs per token
• Every forward+backward through the network touches all parameters.
• Rough rule of thumb: you need O(6) FLOPs per parameter per token
(a couple multiplies/adds in the forward pass, a similar count in the backward, and some small extra for optimizer updates). • So 6 × P FLOPs/token ≃ 6×1.75×10¹¹ ≃1.05×10¹² FLOPs/token.
Total FLOPs
• Multiply FLOPs/token by number of tokens:
Total ≃ (1.05×10¹² FLOPs/token) × (3×10¹¹ tokens)
≃ 3.15×10²³ FLOPs.
Sanity check
• 3×10²³ FLOPs is 3×10⁵ PFLOP·days (since 1 PFLOP/s×86 400 s ≈ 8.6×10¹⁹ FLOPs/day).
• That's a few thousand GPU‐days on a modern accelerator cluster—consistent with the published "thousands of V100‐GPU days" statement.

Bottom‐line estimate: on the order of 10²³–10²⁴ floating‐point operations to train GPT‑3 175 B from scratch.

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2 / 34

02

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025text

Sally has exactly one sister. Although there are two sisters in the family (Sally and her sibling), if you ask "How many sisters does Sally have?" the answer is 1.

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3 / 34

03

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025text

No. As decimal numbers, 9.11 is less than 9.9 (since 0.11 < 0.90), so 9.11 is not greater than 9.9.

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4 / 34

04

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025text

Here are five jokes:

I used to be addicted to soap, but I'm clean now.
Parallel lines have so much in common. It's a shame they'll never meet.
Why don't skeletons fight each other? They don't have the guts.
I bought some shoes from a drug dealer. I don't know what he laced them with, but I've been tripping all day.
How does Moses make his coffee? Hebrews it.

All five jokes are unique.

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5 / 34

05

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025svg

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6 / 34

06

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025svg

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

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Sponsored

7 / 34

07

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025text

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

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8 / 34

08

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025text

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

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9 / 34

09

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.

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025text

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

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10 / 34

10

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

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025website

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11 / 34

11

Pokémon Battle UI Recreationweb design

Recreate an interactive, nostalgic Pokémon battle UI in a single HTML file.

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025website

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

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025website

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

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12 / 34

12

Mario Level UI Recreationweb design

Recreate an interactive, classic Mario level in a single HTML file.

GPT-5 Codex

GPT-5 Codex

Openai · Sep 2025website

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

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OpenAI o4-mini

OpenAI o4-mini

Openai · Apr 2025website

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

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