Comprehensive side-by-side LLM comparison
. Both models have their strengths depending on your specific coding needs.
OpenAI
GPT-5.1 Codex, released by OpenAI in November 2025, is a coding-specialized model from the GPT-5.1 family engineered for software engineering tasks including code generation, multi-file editing, and agentic development. It targets developers and automated coding pipelines requiring a GPT-5.1-generation model tuned for programming.
OpenAI
GPT-OSS-20B is an open-weight large language model with 20 billion parameters from OpenAI's open-source model initiative. It targets deployments requiring a smaller, efficient model that can run on consumer or mid-tier hardware while maintaining strong reasoning and coding capabilities relative to its size.
2 months newer

GPT-OSS-20B
OpenAI
2025-08-05

GPT-5.1 Codex
OpenAI
2025-11
Context window and performance specifications
Available providers and their performance metrics
GPT-5.1 Codex
GPT-OSS-20B
Hugging Face
GPT-5.1 Codex
GPT-OSS-20B
GPT-5.1 Codex
GPT-OSS-20B