GPT-5.1 Chat vs GPT-5.3-Codex
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for GPT-5.1 Chat and GPT-5.3-Codex.
GPT-5.1 Chat
GPT-5.1 Chat (AKA Instant is the fast, lightweight member of the 5.1 family, optimized for low-latency chat while retaining strong general intelligence. It uses adaptive reasoning to selectively “think” on...
GPT-5.3-Codex
GPT-5.3-Codex is OpenAI’s most advanced agentic coding model, combining the frontier software engineering performance of GPT-5.2-Codex with the broader reasoning and professional knowledge capabilities of GPT-5.2. It achieves state-of-the-art results...
Technical Specifications
| Specification | GPT-5.1 Chat | GPT-5.3-Codex |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Context Window | 128,000 tokens | 400,000 tokens |
| Agent Suitability | N/A | N/A |
| Time to First Token (TTFT) | N/A | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | stable | stable |
| API Available | Yes | Yes |
| Released Date | 2025-11-13 | 2026-02-24 |
API Pricing Comparison
Input Price per Million Tokens
GPT-5.1 Chat
$1.25
GPT-5.3-Codex
$1.75
Output Price per Million Tokens
GPT-5.1 Chat
$10.00
GPT-5.3-Codex
$14.00
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Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
GPT-5.1 Chat Quirks & Gotchas
No developer gotchas reported.
GPT-5.3-Codex Quirks & Gotchas
No developer gotchas reported.