+
+
+
+
+
+
+
+
VS
VS
VS
VS
VS
VS
GPT-5.3 Codex vs o3
Comprehensive side-by-side LLM comparison
o3 supports multimodal inputs. Both models have their strengths depending on your specific coding needs.
+
+
+
+
OpenAI
GPT-5.3 Codex, released by OpenAI in February 2026, is a coding-specialized large language model from the GPT-5.3 family. It targets software engineering workflows including automated code generation, test writing, and agentic multi-file editing, built on the incremental improvements of the GPT-5.3 generation.
+
+
+
+
OpenAI
OpenAI o3, released by OpenAI in April 2025, is a large reasoning model that applies extended chain-of-thought processing to deliver improved performance on complex math, science, and coding tasks. It features a 200K token context window and native image understanding, with demonstrated strong results on mathematics and software engineering benchmarks. o3 targets demanding analytical and engineering tasks where deliberate, multi-step reasoning produces significantly better outcomes than direct generation.
9 months newer
o3
OpenAI
2025-04-16
GPT-5.3 Codex
OpenAI
2026-02
Performance Metrics
Context window and performance specifications
Provider Availability & Performance
Available providers and their performance metrics
+
+
+
+
GPT-5.3 Codex
0 providers
+
+
+
+
o3
1 providers
OpenAI
+
+
+
+
GPT-5.3 Codex
Avg Score:0.0%
Providers:0
+
+
+
+
o3
Avg Score:0.0%
Providers:1