Llama 3.1 405B vs Claude Opus 4

Compare Llama 3.1 405B by Meta AI against Claude Opus 4 by Anthropic, context windows of 128K vs 200K, tested across 6 shared challenges. Updated April 2026.

Which is better, Llama 3.1 405B or Claude Opus 4?

Llama 3.1 405B and Claude Opus 4 are both competitive models. Llama 3.1 405B costs $2.7/M input tokens vs $15/M for Claude Opus 4. Context windows: 128K vs 200K tokens. Compare their real outputs side by side below.

Key Differences Between Llama 3.1 405B and Claude Opus 4

Llama 3.1 405B is made by meta while Claude Opus 4 is from anthropic. Llama 3.1 405B has a 128K token context window compared to Claude Opus 4's 200K. On pricing, Llama 3.1 405B costs $2.7/M input tokens vs $15/M for Claude Opus 4.

Our Verdict
Claude Opus 4
Claude Opus 4
Llama 3.1 405B
Llama 3.1 405BRunner-up

No community votes yet. On paper, Claude Opus 4 has the edge — newer, bigger context window.

Llama 3.1 405B is 24x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
40%

Claude Opus 4 uses 444.0x more bold

Llama 3.1 405B
Claude Opus 4
56%Vocabulary64%
15wSentence Length62w
0.41Hedging0.52
0.0Bold4.4
1.9Lists9.1
0.03Emoji0.11
0.00Headings1.87
0.16Transitions0.27
Based on 5 + 16 text responses
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Llama 3.1 405BClaude Opus 4

279 AI models invented the same fake scientist.

We read every word. 250 models. 2.14 million words. This is what we found.

AI Hallucination Index 2026
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