Comprehensive side-by-side LLM comparison
GPT-5.1 leads with 1.8% higher average benchmark score. GPT-5.1 supports multimodal inputs. Both models have their strengths depending on your specific coding needs.
OpenAI
GPT-5 Codex, released by OpenAI in August 2025, is a coding-specialized large language model from the GPT-5 family engineered for software engineering, code generation, and agentic development workflows. It builds on GPT-5's architecture with optimizations targeting multi-file code editing, test generation, and automated debugging. GPT-5 Codex targets developers and agentic coding tools requiring a model tuned specifically for programming tasks.
OpenAI
GPT-5.1, released by OpenAI in November 2025, is a large language model from the GPT-5 family that delivers incremental improvements in reasoning, instruction following, and multimodal understanding over GPT-5. It features a 400K token context window and targets general-purpose development, long-context analysis, and agentic workflows.
3 months newer

GPT-5 Codex
OpenAI
2025-08

GPT-5.1
OpenAI
2025-11
Average performance across 1 common benchmarks
GPT-5 Codex
GPT-5.1
Performance comparison across key benchmark categories
GPT-5 Codex
GPT-5.1
Available providers and their performance metrics
GPT-5 Codex
GPT-5.1
GPT-5 Codex
GPT-5.1