What is the difference between xAI: Grok 4 Fast (free) and OpenAI o4-mini?

xAI: Grok 4 Fast (free) is developed by xAI while OpenAI o4-mini is developed by OpenAI. You can compare their actual outputs across 35 challenges on Rival to see how they differ in practice.

Which is better, xAI: Grok 4 Fast (free) or OpenAI o4-mini?

It depends on your use case. xAI: Grok 4 Fast (free) and OpenAI o4-mini 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 much does xAI: Grok 4 Fast (free) cost compared to OpenAI o4-mini?

xAI: Grok 4 Fast (free) costs $0/M input tokens and OpenAI o4-mini costs $1.1/M input tokens. xAI: Grok 4 Fast (free) is $1.10/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 xAI: Grok 4 Fast (free) and OpenAI o4-mini on Rival?

This page shows a side-by-side comparison of xAI: Grok 4 Fast (free) and OpenAI o4-mini 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 xAI: Grok 4 Fast (free) and OpenAI o4-mini?

xAI: Grok 4 Fast (free) is developed by xAI while OpenAI o4-mini is developed by OpenAI. You can compare their actual outputs across 35 challenges on Rival to see how they differ in practice.

Which is better, xAI: Grok 4 Fast (free) or OpenAI o4-mini?

It depends on your use case. xAI: Grok 4 Fast (free) and OpenAI o4-mini 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 much does xAI: Grok 4 Fast (free) cost compared to OpenAI o4-mini?

xAI: Grok 4 Fast (free) costs $0/M input tokens and OpenAI o4-mini costs $1.1/M input tokens. xAI: Grok 4 Fast (free) is $1.10/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 xAI: Grok 4 Fast (free) and OpenAI o4-mini on Rival?

This page shows a side-by-side comparison of xAI: Grok 4 Fast (free) and OpenAI o4-mini 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.

xAI: Grok 4 Fast (free) vs OpenAI o4-mini: Which Is Better?

Updated Sep 2025

Our Verdict

xAI: Grok 4 Fast (free)

OpenAI o4-miniRunner-up

No community votes yet. On paper, xAI: Grok 4 Fast (free) has the edge — bigger model tier, newer, bigger context window.

Too close to call

API pricing

Cost per 1M tokens

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

OpenAI o4-mini

Input

$1.10

Output

$4.40

Writing DNA

Style Comparison

Similarity

64%

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

xAI: Grok 4 Fast (free)

OpenAI o4-mini

65%Vocabulary73%

13wSentence Length15w

0.56Hedging0.18

1.4Bold0.0

2.5Lists2.1

0.00Emoji0.00

1.58Headings0.00

0.28Transitions0.02

Based on 14 + 10 text responses

Research

What we learned reading every model

xAI: Grok 4 Fast (free) and OpenAI o4-mini 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 Sonnet 4New provider

OpenAI o4-mini vs xAI: Grok 4Cross-provider

Updated Sep 2025

Our Verdict

xAI: Grok 4 Fast (free)

OpenAI o4-miniRunner-up

No community votes yet. On paper, xAI: Grok 4 Fast (free) has the edge — bigger model tier, newer, bigger context window.

Too close to call

API pricing

Cost per 1M tokens

xAI: Grok 4 Fast (free)

Input

$0.000

Output

$0.000

OpenAI o4-mini

Input

$1.10

Output

$4.40

Writing DNA

Style Comparison

Similarity

64%

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

xAI: Grok 4 Fast (free)

OpenAI o4-mini

65%Vocabulary73%

13wSentence Length15w

0.56Hedging0.18

1.4Bold0.0

2.5Lists2.1

0.00Emoji0.00

1.58Headings0.00

0.28Transitions0.02

Based on 14 + 10 text responses

Research

What we learned reading every model

xAI: Grok 4 Fast (free) and OpenAI o4-mini 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 Sonnet 4New provider

OpenAI o4-mini vs xAI: Grok 4Cross-provider