What is the difference between OpenAI: GPT-5.6 Sol and xAI: Grok 4 Fast (free)?

OpenAI: GPT-5.6 Sol is developed by OpenAI while xAI: Grok 4 Fast (free) is developed by xAI. OpenAI: GPT-5.6 Sol has a 1.1M 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, OpenAI: GPT-5.6 Sol or xAI: Grok 4 Fast (free)?

It depends on your use case. OpenAI: GPT-5.6 Sol 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 OpenAI: GPT-5.6 Sol cost compared to xAI: Grok 4 Fast (free)?

OpenAI: GPT-5.6 Sol costs $5/M input tokens and xAI: Grok 4 Fast (free) costs $0/M input tokens. xAI: Grok 4 Fast (free) is $5.00/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 OpenAI: GPT-5.6 Sol and xAI: Grok 4 Fast (free) on Rival?

This page shows a side-by-side comparison of OpenAI: GPT-5.6 Sol 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 OpenAI: GPT-5.6 Sol and xAI: Grok 4 Fast (free)?

OpenAI: GPT-5.6 Sol is developed by OpenAI while xAI: Grok 4 Fast (free) is developed by xAI. OpenAI: GPT-5.6 Sol has a 1.1M 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, OpenAI: GPT-5.6 Sol or xAI: Grok 4 Fast (free)?

It depends on your use case. OpenAI: GPT-5.6 Sol 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 OpenAI: GPT-5.6 Sol cost compared to xAI: Grok 4 Fast (free)?

OpenAI: GPT-5.6 Sol costs $5/M input tokens and xAI: Grok 4 Fast (free) costs $0/M input tokens. xAI: Grok 4 Fast (free) is $5.00/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 OpenAI: GPT-5.6 Sol and xAI: Grok 4 Fast (free) on Rival?

This page shows a side-by-side comparison of OpenAI: GPT-5.6 Sol 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.

OpenAI: GPT-5.6 Sol vs xAI: Grok 4 Fast (free): Which Is Better?

Updated Jul 2026

Our Verdict

OpenAI: GPT-5.6 Sol

xAI: Grok 4 Fast (free)Runner-up

No community votes yet. On paper, OpenAI: GPT-5.6 Sol has the edge — bigger model tier, newer.

Too close to call

API pricing

Cost per 1M tokens

OpenAI: GPT-5.6 Sol

Input

$5.00

Output

$30.00

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

63%

OpenAI: GPT-5.6 Sol uses 3.3x more emoji

OpenAI: GPT-5.6 Sol

xAI: Grok 4 Fast (free)

63%Vocabulary65%

15wSentence Length13w

0.79Hedging0.56

3.4Bold1.4

3.8Lists2.5

0.03Emoji0.00

0.95Headings1.58

0.08Transitions0.28

Based on 27 + 14 text responses

Research

What we learned reading every model

OpenAI: GPT-5.6 Sol 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 Claude Opus 4.1New provider

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

Updated Jul 2026

Our Verdict

OpenAI: GPT-5.6 Sol

xAI: Grok 4 Fast (free)Runner-up

No community votes yet. On paper, OpenAI: GPT-5.6 Sol has the edge — bigger model tier, newer.

Too close to call

API pricing

Cost per 1M tokens

OpenAI: GPT-5.6 Sol

Input

$5.00

Output

$30.00

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

Writing DNA

Style Comparison

Similarity

63%

OpenAI: GPT-5.6 Sol uses 3.3x more emoji

OpenAI: GPT-5.6 Sol

xAI: Grok 4 Fast (free)

63%Vocabulary65%

15wSentence Length13w

0.79Hedging0.56

3.4Bold1.4

3.8Lists2.5

0.03Emoji0.00

0.95Headings1.58

0.08Transitions0.28

Based on 27 + 14 text responses

Research

What we learned reading every model

OpenAI: GPT-5.6 Sol 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 Claude Opus 4.1New provider

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