What is the difference between Grok 4 Fast (free) and Kimi K2.5?

Grok 4 Fast (free) is developed by xAI while Kimi K2.5 is developed by Moonshot AI. Grok 4 Fast (free) has a 2.0M token context window vs Kimi K2.5's 262K. You can compare their actual outputs across 34 challenges on Rival to see how they differ in practice.

Which is better, Grok 4 Fast (free) or Kimi K2.5?

It depends on your use case. Grok 4 Fast (free) and Kimi K2.5 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 Grok 4 Fast (free) cost compared to Kimi K2.5?

Grok 4 Fast (free) costs $0/M input tokens and Kimi K2.5 costs $0.6/M input tokens. Grok 4 Fast (free) is $0.60/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 Grok 4 Fast (free) and Kimi K2.5 on Rival?

This page shows a side-by-side comparison of Grok 4 Fast (free) and Kimi K2.5 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.

Updated Jan 2026

Grok 4 Fast (free)vsKimi K2.5

Grok 4 Fast (free) is cheaper than Kimi K2.5 at $0/M vs $0.6/M input tokens.

Grok 4 Fast (free) and Kimi K2.5 compared across 34 shared prompts
Spec	Grok 4 Fast (free)	Kimi K2.5
Input price	Free	$0.6/M tokens
Output price	Free	$3/M tokens
Context window	2.0M tokens	262K tokens
Weights	—	Open
Free API (OpenRouter)	No	No
Released	Sep 2025	Jan 2026