GPT-5.3 Codex

by OpenAI

GPT-5.3 Codex is a model from OpenAI, released on February 5, 2026. It has a 400K-token context window and can generate up to 128K output tokens. API pricing is $1.75 per 1M input tokens and $14 per 1M output tokens. It ranks #57 of 220 models by Intelligence Score with a score of 36.2.

GPT-5.3-Codex is OpenAI's most capable coding model, combining frontier agentic coding capabilities, improvements in aesthetics, and context compaction. It sets new state-of-the-art results on Terminal-Bench 2.0 (77.3%), OSWorld-Verified (64.7%), and SWE-Lancer IC Diamond (81.4%). First model classified as High capability for cybersecurity under OpenAI's Preparedness Framework. Available in the Codex app and API.

Key specs

ProviderOpenAI
Release date2026-02-05
Licenseproprietary
Context window400K tokens
Max output128K tokens
Input price$1.75 / 1M tokens
Output price$14 / 1M tokens
Intelligence Score36.2
Coding index29.4

Quick answers

What is the context window of GPT-5.3 Codex?

GPT-5.3 Codex has a context window of 400K tokens, with a maximum output of 128K tokens per response.

How much does GPT-5.3 Codex cost?

GPT-5.3 Codex costs $1.75 per 1M input tokens and $14 per 1M output tokens through the API.

Is GPT-5.3 Codex open source?

No. GPT-5.3 Codex is a proprietary model from OpenAI (proprietary license).

When was GPT-5.3 Codex released?

OpenAI released GPT-5.3 Codex on February 5, 2026.

How does GPT-5.3 Codex compare to Claude Opus 5.5 (Reasoning)?

GPT-5.3 Codex scores 36.2 on the Intelligence Score versus 60.5 for Claude Opus 5.5 (Reasoning), the current #1. Input pricing is $1.75 vs $4 per 1M tokens.

Compare on the AI leaderboard · All AI models

More models from OpenAI