Compare models
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 o3OpenAI | GPT-5.5 OpenAI |  DeepSeek-V4-FlashDeepSeek | |
|---|---|---|---|
| Vendor | OpenAI | OpenAI | DeepSeek |
| Family | o-series | GPT | DeepSeek |
| Release date | 2025-04-16 | 2026-04-23 | 2026-04-22 |
| Context window | 200,000 tokens | 400,000 tokens | 1,000,000 tokens |
| Parameters | — | — | 284B (13B active) |
| Modality | text, vision | text, vision, audio | text |
| License | proprietary | proprietary | MIT |
| Source | proprietary | proprietary | open weights |
| Description | Reasoning-focused model in the o-series. | OpenAI's smartest and most intuitive model — successor to GPT-5, with major coding, research, and document workflow gains. GPT-5.5 Pro variant also available for heavier reasoning. | Smaller, faster sibling to DeepSeek-V4-Pro. Same 1M context window with a much lighter 284B / 13B-active MoE. |
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