GPT-5.1 vs GPT OSS 20B

Compare GPT-5.1 and GPT OSS 20B, both from OpenAI, context windows of 400K vs 131K, tested across 52 shared challenges. Updated April 2026.

Which is better, GPT-5.1 or GPT OSS 20B?

GPT-5.1 and GPT OSS 20B are both competitive models. GPT-5.1 costs $1.25/M input tokens vs $0.02/M for GPT OSS 20B. Context windows: 400K vs 131K tokens. Compare their real outputs side by side below.

Key Differences Between GPT-5.1 and GPT OSS 20B

GPT-5.1 is made by openai while GPT OSS 20B is from openai. GPT-5.1 has a 400K token context window compared to GPT OSS 20B's 131K. On pricing, GPT-5.1 costs $1.25/M input tokens vs $0.02/M for GPT OSS 20B.

Our Verdict
GPT-5.1
GPT-5.1
GPT OSS 20B
GPT OSS 20BRunner-up

No community votes yet. On paper, GPT-5.1 has the edge — bigger model tier, newer, bigger context window.

GPT OSS 20B is 100x cheaper per token — worth considering if cost matters.

Slight edge
Writing DNA

Style Comparison

Similarity
100%

GPT OSS 20B uses 10.2x more emoji

GPT-5.1
GPT OSS 20B
62%Vocabulary54%
19wSentence Length17w
0.29Hedging0.26
3.5Bold5.9
7.2Lists3.3
0.00Emoji0.10
0.61Headings0.75
0.03Transitions0.32
Based on 14 + 21 text responses
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GPT-5.1GPT OSS 20B

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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