GPT-5.1 Codex vs DeepSeek R2 for coding
GPT-5.1 Codex is the stronger coder of the two on benchmarks, but DeepSeek R2 can be the better pick when cost, speed, or context window matter more. Below: a side-by-side spec table and exactly when to pick each.
At a glance
| Spec | GPT-5.1 Codex | DeepSeek R2 |
|---|---|---|
| Provider | OpenAI | DeepSeek |
| Released | Nov 2025 | Feb 2026 |
| SWE-bench Verified | 75% | 55% |
| HumanEval | 95% | 93% |
| MMLU | 88% | 86% |
| Context window | 400K | 128K |
| Max output | 128K | 32K |
| Input price (per 1M) | $1.25 | $0.40 |
| Output price (per 1M) | $10 | $1.50 |
| Price tier | Mid | Budget |
| Speed | Medium | Slow/Reasoning |
| Hosting | Closed/API | Closed/API |
| Modality | Text + Vision | Text-only |
| Knowledge cutoff | Oct 2025 | Dec 2025 |
Pick GPT-5.1 Codex if…
- It scores higher on SWE-bench Verified (75% vs 55%), the best proxy for real-world coding.
- It has a larger context window (400K vs 128K).
- It responds faster (Medium).
- It's tuned for codex CLI and long-horizon coding agents; engineered for terminal-driven workflows.
Pick DeepSeek R2 if…
- It's cheaper (Budget tier vs Mid).
- It's tuned for hard reasoning at 1/20th o3 cost, math (AIME 83.2%, MATH 98.1%), competitive programming, research-grade analysis on a budget.
GPT-5.1 Codex vs DeepSeek R2: which is better for coding?
GPT-5.1 Codex is the stronger coder of the two on benchmarks, but DeepSeek R2 can be the better pick when cost, speed, or context window matter more. See the full spec table for SWE-bench, HumanEval, MMLU, context window, and pricing on both. Benchmarks are a directional signal, not a guarantee for your codebase — the most reliable test is running both on a real task you care about.
Compare these head-to-head with live data, or build a full stack around your pick — Flowpicker shows compatibility and monthly cost.
Open the live comparison →More comparisons
See the full model leaderboard ranked by SWE-bench, HumanEval, and MMLU.