GPT-5.1-Codex
GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks. The model supports building projects from scratch, feature development, debugging, large-scale refactoring, and code review. Compared to GPT-5.1, Codex is more steerable, adheres closely to developer instructions, and produces cleaner, higher-quality code outputs. Reasoning
Context window
This model accepts 400K tokens in one request (~300K words of text).
What fits in one request
- FitsShort documentAbout 1,500 words of text
- FitsLong documentAbout 37K words of text
- FitsSmall codebaseAbout 150K words of text
- Won't fitFull novelAbout 375K words of text
Specifications
Context size, pricing, and release info in one place.
- Context window
- 400,000 tokens (400K)
- Max output tokens
- 128,000 tokens (128K)
- Speed tier
- balanced
- Provider
- Openai
- Release date
- Nov 2025
Capabilities
See which features this model supports, such as vision, tools, and streaming.
- Vision
- Accepts image inputs alongside text
- Supported
- Tool use
- Can call external tools and APIs
- Supported
- Function calling
- Structured function call interface
- Supported
- Extended thinking
- Shows its chain-of-thought reasoning
- Supported
- Streaming
- Returns tokens as they are generated
- Supported
- Prompt caching
- Reuse repeated prompt prefixes cheaply
- Supported
- Web search
- Can browse the web during a request
- Not supported
- Batch API
- Process many requests asynchronously
- Not supported
Best for
Jump to a guide or ranking that matches each workload.
Compare GPT-5.1-Codex
Open a side-by-side comparison with one click.
- GPT-5.1-Codex vs Amazon Titan Text Express
GPT-5.1-Codex has 852% larger context window
- GPT-5.1-Codex vs Amazon Titan Text Lite
GPT-5.1-Codex has 852% larger context window
- GPT-5.1-Codex vs Amazon Titan Text Premier
GPT-5.1-Codex has 852% larger context window
- GPT-5.1-Codex vs Claude Instant
GPT-5.1-Codex has 300% larger context window
- GPT-5.1-Codex vs Anthropic Claude
GPT-5.1-Codex has 300% larger context window
- GPT-5.1-Codex vs Codellama 34b Instruct
GPT-5.1-Codex has 9665% larger context window
Frequently asked questions
Short answers about context size and how this model behaves.
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