What is the difference between Claude Opus 4.5 and xAI: Grok 4 Fast (free)?

Claude Opus 4.5 is developed by Anthropic while xAI: Grok 4 Fast (free) is developed by xAI. You can compare their actual outputs across 35 challenges on Rival to see how they differ in practice.

Which is better, Claude Opus 4.5 or xAI: Grok 4 Fast (free)?

It depends on your use case. Claude Opus 4.5 and xAI: Grok 4 Fast (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 35 challenges so you can judge which fits your needs best.

How can I compare Claude Opus 4.5 and xAI: Grok 4 Fast (free) on Rival?

This page shows a side-by-side comparison of Claude Opus 4.5 and xAI: Grok 4 Fast (free) 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.

What is the difference between Claude Opus 4.5 and xAI: Grok 4 Fast (free)?

Claude Opus 4.5 is developed by Anthropic while xAI: Grok 4 Fast (free) is developed by xAI. You can compare their actual outputs across 35 challenges on Rival to see how they differ in practice.

Which is better, Claude Opus 4.5 or xAI: Grok 4 Fast (free)?

It depends on your use case. Claude Opus 4.5 and xAI: Grok 4 Fast (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 35 challenges so you can judge which fits your needs best.

How can I compare Claude Opus 4.5 and xAI: Grok 4 Fast (free) on Rival?

This page shows a side-by-side comparison of Claude Opus 4.5 and xAI: Grok 4 Fast (free) 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.

Claude Opus 4.5 vs xAI: Grok 4 Fast (free): Which Is Better?

Updated Nov 2025

Our Verdict

Claude Opus 4.5

xAI: Grok 4 Fast (free)Runner-up

No community votes yet. On paper, Claude Opus 4.5 has the edge — bigger model tier, newer.

Too close to call

API pricing

Cost per 1M tokens

Claude Opus 4.5

Input

—

Output

—

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

40%

Claude Opus 4.5 uses 15.2x more emoji

Claude Opus 4.5

xAI: Grok 4 Fast (free)

64%Vocabulary65%

55wSentence Length13w

0.86Hedging0.56

5.8Bold1.4

4.5Lists2.5

0.15Emoji0.00

1.59Headings1.58

0.05Transitions0.28

Based on 24 + 14 text responses

Research

What we learned reading every model

Claude Opus 4.5 and xAI: Grok 4 Fast (free) have opinions about your brand too.Ask 10 models what they tell people about you. Verbatim receipts.Run the mirror

FAQ

Common questions

Keep exploring

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xAI: Grok 4 Fast (free) vs OpenAI o3New provider

xAI: Grok 4 Fast (free) vs Llama 4 MaverickNew provider

Updated Nov 2025

Our Verdict

Claude Opus 4.5

xAI: Grok 4 Fast (free)Runner-up

No community votes yet. On paper, Claude Opus 4.5 has the edge — bigger model tier, newer.

Too close to call

API pricing

Cost per 1M tokens

Claude Opus 4.5

Input

—

Output

—

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

40%

Claude Opus 4.5 uses 15.2x more emoji

Claude Opus 4.5

xAI: Grok 4 Fast (free)

64%Vocabulary65%

55wSentence Length13w

0.86Hedging0.56

5.8Bold1.4

4.5Lists2.5

0.15Emoji0.00

1.59Headings1.58

0.05Transitions0.28

Based on 24 + 14 text responses

Research

What we learned reading every model

Claude Opus 4.5 and xAI: Grok 4 Fast (free) have opinions about your brand too.Ask 10 models what they tell people about you. Verbatim receipts.Run the mirror

FAQ

Common questions

Keep exploring

More comparisons

xAI: Grok 4 Fast (free) vs MiniMax M3New provider

xAI: Grok 4 Fast (free) vs OpenAI o3New provider

xAI: Grok 4 Fast (free) vs Llama 4 MaverickNew provider