xAI: Grok 4 Fast (free) vs OpenAI o3
Compare xAI: Grok 4 Fast (free) by xAI against OpenAI o3 by OpenAI, tested across 35 shared challenges. Updated May 2026.
Which is better, xAI: Grok 4 Fast (free) or OpenAI o3?
xAI: Grok 4 Fast (free) and OpenAI o3 are both competitive models. xAI: Grok 4 Fast (free) costs $0/M input tokens vs $10/M for OpenAI o3. Compare their real outputs side by side below.
Key Differences Between xAI: Grok 4 Fast (free) and OpenAI o3
xAI: Grok 4 Fast (free) is made by xai while OpenAI o3 is from openai. On pricing, xAI: Grok 4 Fast (free) costs $0/M input tokens vs $10/M for OpenAI o3.
API pricing
Per 1M tokens
xAI: Grok 4 Fast (free)
Input
$0.000
Output
$0.000
OpenAI o3
Input
$10.00
Output
$40.00
Our Verdict
xAI: Grok 4 Fast (free)
OpenAI o3
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
Writing DNA
Style Comparison
Similarity
64%
xAI: Grok 4 Fast (free) uses 4.2x more headings
xAI: Grok 4 Fast (free)
OpenAI o3
65%Vocabulary68%
13wSentence Length14w
0.56Hedging0.26
1.4Bold0.7
2.5Lists3.0
0.00Emoji0.00
1.58Headings0.38
0.28Transitions0.12
Based on 14 + 16 text responses
FAQ
