OpenAI Codex (2021)

Name: OpenAI Codex (2021)
Author: OpenAI

Closed

OpenAI's 2021 code-generation model - a GPT-3 fine-tune on public GitHub code that powered the original GitHub Copilot launch (distinct from the 2025 Codex CLI agent).

Open

Publisher: OpenAI
Family: GPT
Params: 12B (Codex-12B), with smaller 300M and 2.5B variants reported
Context: 4K
Input
Output
Providers: openai
License: Proprietary
Released: Jul 2021
Canonical: openai.com/index/openai-codex

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Notes

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Context

Reported eval scores

No public eval scores tracked.

Introduced in

paperEvaluating Large Language Models Trained on Code