Claude Opus 5.5vsGrok 4 Fast (free)

Claude Opus 5.5 is developed by Anthropic while Grok 4 Fast (free) is developed by xAI. Claude Opus 5.5 has a 1.0M token context window vs Grok 4 Fast (free)'s 2.0M. You can compare their actual outputs across 2 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Opus 5.5 and Grok 4 Fast (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 2 challenges so you can judge which fits your needs best.

Claude Opus 5.5 costs $4/M input tokens and Grok 4 Fast (free) costs $0/M input tokens. Grok 4 Fast (free) is $4.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of Claude Opus 5.5 and 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.