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

Claude Opus 4 is developed by Anthropic while xAI: Grok 4 Fast (free) is developed by xAI. Claude Opus 4 has a 200K token context window vs xAI: Grok 4 Fast (free)'s 2.0M. You can compare their actual outputs across 34 challenges on Rival to see how they differ in practice.

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

It depends on your use case. Claude Opus 4 and xAI: Grok 4 Fast (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 34 challenges so you can judge which fits your needs best.

How much does Claude Opus 4 cost compared to xAI: Grok 4 Fast (free)?

Claude Opus 4 costs $15/M input tokens and xAI: Grok 4 Fast (free) costs $0/M input tokens. xAI: Grok 4 Fast (free) is $15.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

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

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

Claude Opus 4 is developed by Anthropic while xAI: Grok 4 Fast (free) is developed by xAI. Claude Opus 4 has a 200K token context window vs xAI: Grok 4 Fast (free)'s 2.0M. You can compare their actual outputs across 34 challenges on Rival to see how they differ in practice.

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

It depends on your use case. Claude Opus 4 and xAI: Grok 4 Fast (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 34 challenges so you can judge which fits your needs best.

How much does Claude Opus 4 cost compared to xAI: Grok 4 Fast (free)?

Claude Opus 4 costs $15/M input tokens and xAI: Grok 4 Fast (free) costs $0/M input tokens. xAI: Grok 4 Fast (free) is $15.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

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

This page shows a side-by-side comparison of Claude Opus 4 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 vs xAI: Grok 4 Fast (free): Which Is Better?

Updated Sep 2025

Our Verdict

Claude Opus 4

xAI: Grok 4 Fast (free)

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

API pricing

Cost per 1M tokens

Claude Opus 4

Input

$15.00

Output

$75.00

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

48%

Claude Opus 4 uses 11.2x more emoji

Claude Opus 4

xAI: Grok 4 Fast (free)

64%Vocabulary65%

62wSentence Length13w

0.52Hedging0.56

4.4Bold1.4

9.1Lists2.5

0.11Emoji0.00

1.87Headings1.58

0.27Transitions0.28

Based on 16 + 14 text responses

Research

What we learned reading every model

Claude Opus 4 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 GPT-5New provider

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

Updated Sep 2025

Our Verdict

Claude Opus 4

xAI: Grok 4 Fast (free)

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

API pricing

Cost per 1M tokens

Claude Opus 4

Input

$15.00

Output

$75.00

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

48%

Claude Opus 4 uses 11.2x more emoji

Claude Opus 4

xAI: Grok 4 Fast (free)

64%Vocabulary65%

62wSentence Length13w

0.52Hedging0.56

4.4Bold1.4

9.1Lists2.5

0.11Emoji0.00

1.87Headings1.58

0.27Transitions0.28

Based on 16 + 14 text responses

Research

What we learned reading every model

Claude Opus 4 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 GPT-5New provider

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