What is the difference between GPT-5 Pro and xAI: Grok 4 Fast (free)?

GPT-5 Pro is developed by OpenAI while xAI: Grok 4 Fast (free) is developed by xAI. GPT-5 Pro has a 400K token context window vs xAI: Grok 4 Fast (free)'s 2.0M. You can compare their actual outputs across 24 challenges on Rival to see how they differ in practice.

Which is better, GPT-5 Pro or xAI: Grok 4 Fast (free)?

It depends on your use case. GPT-5 Pro and xAI: Grok 4 Fast (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 24 challenges so you can judge which fits your needs best.

How much does GPT-5 Pro cost compared to xAI: Grok 4 Fast (free)?

GPT-5 Pro 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 GPT-5 Pro and xAI: Grok 4 Fast (free) on Rival?

This page shows a side-by-side comparison of GPT-5 Pro 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 GPT-5 Pro and xAI: Grok 4 Fast (free)?

GPT-5 Pro is developed by OpenAI while xAI: Grok 4 Fast (free) is developed by xAI. GPT-5 Pro has a 400K token context window vs xAI: Grok 4 Fast (free)'s 2.0M. You can compare their actual outputs across 24 challenges on Rival to see how they differ in practice.

Which is better, GPT-5 Pro or xAI: Grok 4 Fast (free)?

It depends on your use case. GPT-5 Pro and xAI: Grok 4 Fast (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 24 challenges so you can judge which fits your needs best.

How much does GPT-5 Pro cost compared to xAI: Grok 4 Fast (free)?

GPT-5 Pro 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 GPT-5 Pro and xAI: Grok 4 Fast (free) on Rival?

This page shows a side-by-side comparison of GPT-5 Pro 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.

GPT-5 Pro vs xAI: Grok 4 Fast (free): Which Is Better?

Updated Oct 2025

Our Verdict

GPT-5 Pro

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

GPT-5 Pro

Input

$15.00

Output

$120.00

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

60%

xAI: Grok 4 Fast (free) uses 138.0x more bold

GPT-5 Pro

xAI: Grok 4 Fast (free)

65%Vocabulary65%

15wSentence Length13w

0.32Hedging0.56

0.0Bold1.4

2.9Lists2.5

0.00Emoji0.00

0.00Headings1.58

0.01Transitions0.28

Based on 11 + 14 text responses

Research

What we learned reading every model

GPT-5 Pro 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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GPT-5 Pro vs MiniMax M3New provider

GPT-5 Pro vs Llama 4 MaverickNew provider

GPT-5 Pro vs Gemini 2.5 Pro (I/O Edition)New provider

Updated Oct 2025

Our Verdict

GPT-5 Pro

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

GPT-5 Pro

Input

$15.00

Output

$120.00

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

60%

xAI: Grok 4 Fast (free) uses 138.0x more bold

GPT-5 Pro

xAI: Grok 4 Fast (free)

65%Vocabulary65%

15wSentence Length13w

0.32Hedging0.56

0.0Bold1.4

2.9Lists2.5

0.00Emoji0.00

0.00Headings1.58

0.01Transitions0.28

Based on 11 + 14 text responses

Research

What we learned reading every model

GPT-5 Pro 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

GPT-5 Pro vs MiniMax M3New provider

GPT-5 Pro vs Llama 4 MaverickNew provider

GPT-5 Pro vs Gemini 2.5 Pro (I/O Edition)New provider