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Step 5 Preview
GPT-5.3-Codex
GPT-5.3-Codex is a proprietary model from OpenAI, released Feb 24, 2026. Its best result is #16 of 143 on LiveCodeBench with 87.31%. It costs $1.75 per million input tokens and $14 per million output tokens, with a 400K-token context window.
- Developer
- OpenAI
- Released
- Feb 24, 2026
- Context window
- 400K
- Price in / out, per 1M tokens
- $1.75 / $14
- Weights
- Proprietary
- Inputs
- Text, Images, Files
- Reasoning
- Yes
- Tool use
- Yes
Benchmarks
| Benchmark | Score bar | Accuracy | Rank | Cost / test |
|---|---|---|---|---|
| SWE-benchCoding | 78.00% | 32 / 85 | $0.46 | |
| Vibe Code BenchCoding | 61.77% | 52 / 115 | $11.91 | |
| LiveCodeBenchCoding | 87.31% | 16 / 143 | $1.75 / $14 |
Vals AI, as of Oct 24, 2026.
LMArena, by category
| Leaderboard | Rating | Rank | Votes |
|---|---|---|---|
| WebDevLMArena | 1407 | 94 / 124 | 2.6K |
LMArena, CC BY 4.0, as of Oct 22, 2026. Where a model is rated at several effort levels, its best is shown.
Compare GPT-5.3-Codex
OpenAI
The lab behind GPT and ChatGPT, which brought large language models to hundreds of millions of people. Founded 2015, based in San Francisco. openai.com
Questions
Who makes GPT-5.3-Codex?
GPT-5.3-Codex is made by OpenAI, founded 2015 and based in San Francisco.
How much does GPT-5.3-Codex cost?
$1.75 per million input tokens and $14 per million output tokens, at its provider’s list price.
What is GPT-5.3-Codex’s context window?
400K tokens (400,000).
Is GPT-5.3-Codex open source?
No. GPT-5.3-Codex is proprietary and served through its provider’s API.