Updated Sep 19, 2025

Our Verdict

xAI: Grok 4 Fast (free)

Claude Opus 4

No community votes yet. On paper, these are closely matched - try both with your actual task to see which fits your workflow.

Too close to call

Writing DNA

Style Comparison

Similarity

79%

Claude Opus 4 uses 11.2x more emoji

xAI: Grok 4 Fast (free)

Claude Opus 4

65%Vocabulary64%

13wSentence Length62w

0.56Hedging0.52

1.4Bold4.4

2.5Lists9.1

0.00Emoji0.11

1.58Headings1.87

0.28Transitions0.27

Based on 14 + 16 text responses

vs

Ask them anything yourself

xAI: Grok 4 Fast (free)

Claude Opus 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

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

FAQ

Common questions

Keep going

xAI: Grok 4 Fast (free) vs MiniMax M1New provider

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

xAI: Grok 4 Fast (free) vs Claude Sonnet 4Cross-provider

xAI: Grok 4 Fast (free)vsClaude Opus 4

21 fights queued

Why xAI: Grok 4 Fast (free)?

10x more context2.0M

4 months newerSep 2025

Why Claude Opus 4?

Dead even. This one's a coin flip.

xAI: Grok 4 Fast (free)Claude Opus 4

Input price

$0.000/M

$15.00/M

Output price

$0.000/M

$75.00/M

Context

2.0M

200K

Released

Sep 2025

May 2025

Favorites

xAI: Grok 4 Fast (free)Claude Opus 4

Movie

—

Arrival

Arrival

Album

—

The Dark Side of the Moon

The Dark Side of the Moon

Book

—

Cien años de soledad

Cien años de soledad

Gabriel García Márquez

City

—

Istanbul

Game

—

Portal 2

Portal 2

Shooter, Puzzle4.6

12 / 21

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 Opus 4

Claude Opus 4

Anthropic · May 2025text

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

Given information:

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

Since Sally is one of the sisters that each brother has, and each brother has 2 sisters total, that means th ere must be exactly 2 sisters in the family.

The 2 sisters are:

Sally
One other sister

Therefore, Sally has 1 sister.

Try this prompt

Vote

2 / 21

02

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!

Try this prompt

Claude Opus 4

Claude Opus 4

Anthropic · May 2025text

Here are 5 jokes:

Why don't scientists trust atoms? Because they make up everything!
What do you call a bear with no teeth? A gummy bear!
Why did the scarecrow win an award? He was outstanding in his field!
What do you call a fake noodle? An impasta!
Why don't eggs tell jokes? They'd crack up!

All 5 jokes are unique - each one has a different setup and punchline, covering different topics (atoms/scie nce, bears, scarecrows, pasta, and eggs).

Try this prompt

Vote

3 / 21

03

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

Try this prompt

Claude Opus 4

Claude Opus 4

Anthropic · May 2025svg

Try this prompt

Vote

4 / 21

04

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 Opus 4

Claude Opus 4

Anthropic · May 2025svg

Try this prompt

Vote

5 / 21

05

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 Opus 4

Claude Opus 4

Anthropic · May 2025text

"Modern Life is Weird"

[Walk on stage]

You know what's crazy about being an adult? Nobody tells you that half of it is just googling things you're too embarrassed to ask real people. Last week I googled "is it normal for my knee to sound like bubble wrap? " The answer was either "yes, totally fine" or "you have six weeks to live." Thanks, internet!

[Pause]

I went to the doctor about it. You know you're getting old when your doctor looks like they should be asking YOU for ID to buy alcohol. This kid walks in with a stethoscope, and I'm like, "Did you just graduate... fr om middle school?"

But here's what really gets me – why do we act completely insane at the doctor's office? They ask, "How much do you drink?" and suddenly I'm doing calculus in my head. "Well, let's see, carry the one... I have a glas s of wine with dinner." Yeah, a glass. It's just a really big glass. It's a vase, actually. I drink wine fro m a vase.

[Mime drinking from large container]

And don't get me started on grocery shopping. Why do I need a PhD to buy shampoo? There's moisturizing, volu mizing, clarifying, fortifying... I just want my hair to be clean! I don't need it to solve my emotional pro blems!

Plus, self-checkout is a trap. They put you in charge of scanning your own groceries like you work there. Th en the machine starts screaming "UNEXPECTED ITEM IN BAGGING AREA!" Yeah, it's unexpected because I don't wor k here! I'm doing my best, robot!

[Pause for effect]

The worst part is when you're buying embarrassing things. Last week I had toilet paper, ice cream, and cat f ood. The machine froze, and the teenage employee had to come over. He looked at my items and I could see him thinking, "This person's having a rough week."

[Shrug]

Speaking of technology, my phone knows too much about me. It autocorrects "running late" before I even type it because that's apparently my catchphrase now. My maps app just assumes I'm lost. It doesn't even wait for me to ask for directions anymore. I'll be sitting on my couch and it's like, "Turn right to get to your kit chen."

And what's with password requirements these days? "Must contain uppercase, lowercase, numbers, symbols, the blood of your firstborn, and a haiku about your childhood fears." Then they're like, "Don't write it down!" Where am I supposed to store this information? I can't remember why I walked into a room!

[Pace across stage]

You know what else nobody prepared me for? How excited I'd get about cancelled plans. Someone texts "Hey, ca n we raincheck?" and I'm already in my pajamas like "Oh no! What a shame! I was so looking forward to puttin g on real pants!"

Because going out now requires preparation. I need three business days' notice. I need to charge my social b attery. I need to practice conversation topics. Remember when we could just... show up places?

[Final beat]

The truth is, we're all just walking around pretending we know what we're doing. But at least we're all conf used together. And hey, if you ever see someone at the store at 10 PM buying wine in a box and googling "why does my back hurt when I breathe?" – just give them a nod. We're all in this together.

[Pause]

Thank you, you've been a wonderful audience! Don't forget to validate your parking – unlike my life choices!

[Exit]

Try this prompt

Vote

6 / 21

06

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 Opus 4

Claude Opus 4

Anthropic · May 2025website

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

Try this prompt

Vote

Sponsored

7 / 21

07

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 Opus 4

Claude Opus 4

Anthropic · May 2025website

Try this prompt

Vote

8 / 21

08

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 Opus 4

Claude Opus 4

Anthropic · May 2025website

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

Try this prompt

Vote

9 / 21

09

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 Opus 4

Claude Opus 4

Anthropic · May 2025svg

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

Try this prompt

Vote

10 / 21

10

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 Opus 4

Claude Opus 4

Anthropic · May 2025website

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

Try this prompt

Vote

11 / 21

11

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 Opus 4

Claude Opus 4

Anthropic · May 2025svg

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

Try this prompt

Vote

12 / 21

12

Simple 7-Ingredient Recipeconversation

Generate a unique and simple recipe with common ingredients.

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 Opus 4

Claude Opus 4

Anthropic · May 2025text

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

Try this prompt

Vote

This matchup has more rounds

9+ more head-to-head results. Free. Not a trick.

Free account. No card required. By continuing, you agree to Rival's Terms and Privacy Policy