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GPT-5.3 Codex vs o3 Pro
Comprehensive side-by-side LLM comparison
o3 Pro supports multimodal inputs. Both models have their strengths depending on your specific coding needs.
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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.
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OpenAI
OpenAI o3-pro, released by OpenAI in June 2025, is an extended reasoning model from the o3 family that applies more compute per response to deliver deeper, more thorough answers on complex problems. It features a 200K token context window, 100K maximum output tokens, and vision capabilities. o3-pro targets research-grade reasoning tasks, extended coding sessions, and applications where accuracy on difficult problems justifies higher inference cost and latency.
7 months newer
o3 Pro
OpenAI
2025-06-10
GPT-5.3 Codex
OpenAI
2026-02
Performance Metrics
Context window and performance specifications
Provider Availability & Performance
Available providers and their performance metrics
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GPT-5.3 Codex
0 providers
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o3 Pro
1 providers
OpenAI
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GPT-5.3 Codex
Avg Score:0.0%
Providers:0
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o3 Pro
Avg Score:0.0%
Providers:1