Updated Sep 19, 2025

Our Verdict

xAI: Grok 4 Fast (free)

Claude Sonnet 4Runner-up

No community votes yet. On paper, xAI: Grok 4 Fast (free) has the edge — newer, bigger context window.

Too close to call

Writing DNA

Style Comparison

Similarity

79%

Claude Sonnet 4 uses 87.9x more emoji

xAI: Grok 4 Fast (free)

Claude Sonnet 4

65%Vocabulary62%

13wSentence Length111w

0.56Hedging0.40

1.4Bold5.0

2.5Lists9.3

0.00Emoji0.88

1.58Headings2.16

0.28Transitions0.33

Based on 14 + 17 text responses

vs

Ask them anything yourself

xAI: Grok 4 Fast (free)

Claude Sonnet 4

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

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FAQ

Common questions

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xAI: Grok 4 Fast (free) vs MiniMax M2.5New provider

xAI: Grok 4 Fast (free) vs Aurora AlphaNew provider

xAI: Grok 4 Fast (free) vs GPT-5New provider

xAI: Grok 4 Fast (free)vsClaude Sonnet 4

20 fights queued

Why xAI: Grok 4 Fast (free)?

10x more context2.0M

4 months newerSep 2025

Why Claude Sonnet 4?

Dead even. This one's a coin flip.

xAI: Grok 4 Fast (free)Claude Sonnet 4

Input price

$0.000/M

$3.00/M

Output price

$0.000/M

$15.00/M

Context

2.0M

200K

Released

Sep 2025

May 2025

Favorites

xAI: Grok 4 Fast (free)Claude Sonnet 4

Movie

—

2001: A Space Odyssey

2001: A Space Odyssey

Album

—

Kind of Blue

Book

—

Gödel, Escher, Bach

Gödel, Escher, Bach

Douglas R. Hofstadter

City

—

Istanbul

Game

—

Portal 2

Portal 2

Shooter, Puzzle4.6

12 / 20

01

Logic Puzzlereasoning

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

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025text

1

Sally has 1 sister. The family consists of 3 brothers and 2 sisters (Sally and one other). Each brother thus has 2 sisters, which matches the given information.

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025text

I need to think through this step-by-step.

Given information:

Sally is a girl
Sally has 3 brothers
Each brother has 2 sisters

Let me work out how many sisters are in the family total.

If each of Sally's 3 brothers has 2 sisters, and all the brothers are in the same family, then there must be 2 sisters total in the family.

Since Sally is one of those sisters, and there are 2 sisters total, Sally must have 1 sister.

Therefore, Sally has 1 sister.

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2 / 20

02

Math Misconception Testreasoning

Tests an AI's understanding of number representation

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025text

No, 9.11 is less than 9.9 (which is equivalent to 9.90).

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025text

No, 9.11 is not greater than 9.9.

To compare these decimal numbers:

9.11 = 9.11
9.9 = 9.90

Since both numbers have the same whole number part (9), we compare the decimal parts:

0.11 vs 0.90
11 hundredths vs 90 hundredths

Therefore, 9.9 is greater than 9.11.

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3 / 20

03

Stochastic Consistency Testanalysis

Tests an AI's randomness and creativity

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025text

5 Jokes

Why don't skeletons fight each other? They don't have the guts!
What do you call a bear with no teeth? A gummy bear!
Why did the math book look sad? Because it had too many problems.
How do you organize a space party? You planet!
Why couldn't the leopard play hide and seek? Because he was always spotted!

How Many Are Unique?

All 5 are unique—no duplicates here!

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Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025text

Here are 5 jokes for you:

Why don't scientists trust atoms? Because they make up everything!
I told my wife she was drawing her eyebrows too high. She looked surprised.
Why don't eggs tell jokes? They'd crack each other up!
I'm reading a book about anti-gravity. It's impossible to put down!
Why did the scarecrow win an award? He was outstanding in his field!

All 5 jokes are unique - each one has a different setup, punchline, and comedic concept. They cover different types of wordplay: scientific puns (#1, #4), visual humor (#2), food puns (#3), and agricultural wordplay (#5).

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4 / 20

04

SVG Layout Challengeimage generation

Tests an AI's ability to generate vector graphics

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025svg

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Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025svg

Try this prompt

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5 / 20

05

Xbox Controller SVG Artimage generation

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

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025svg

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025svg

Try this prompt

Vote

6 / 20

06

Generate a Stand-Up Routineconversation

Tests an AI's humor and creative writing ability

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025text

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

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025text

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

Try this prompt

Vote

Sponsored

7 / 20

07

Pokémon Battle UI Recreationweb design

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

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025website

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

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025website

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

Try this prompt

Vote

8 / 20

08

Linear App Cloneweb design

Tests an AI's ability to replicate an existing UI with Tailwind CSS

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025website

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

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025website

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

Try this prompt

Vote

9 / 20

09

Interactive Catan Boardweb design

Tests an AI's ability to create interactive web elements

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025website

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

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025website

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

Try this prompt

Vote

10 / 20

10

World Map SVGimage generation

Tests an AI's ability to create a detailed world map in SVG format

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025svg

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

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025svg

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

Try this prompt

Vote

11 / 20

11

Random Tailwind Webappweb design

Generate a single-page, self-contained HTML webapp using Tailwind CSS for a randomly chosen category/industry/niche.

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025website

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

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025website

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

Try this prompt

Vote

12 / 20

12

Surprise Animal SVGimage generation

Generate SVG art of a randomly chosen animal in a setting of its choosing.

xAI: Grok 4 Fast (free)

xAI: Grok 4 Fast (free)

Xai · Sep 2025svg

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

Try this prompt

Claude Sonnet 4

Claude Sonnet 4

Anthropic · May 2025svg

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

Try this prompt

Vote

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