SIDE BY SIDE
Gemini 3.1 Pro Preview vs Gemini 3.5 Flash
Both are Gemini models. Gemini 3.5 Flash was added to OpenRouter on 2026-05-19, Gemini 3.1 Pro Preview on 2026-02-19.
| Field | Gemini 3.1 Pro Preview | Gemini 3.5 Flash |
|---|---|---|
| Provider | ||
| Family | Gemini | Gemini |
| Province | The High Peaks | The High Peaks |
| Context window | 1.05M tokens | 1.05M tokens |
| Maximum output | 66K tokens | 66K tokens |
| Input / 1M tokens | $2.00 | $1.50 |
| Output / 1M tokens | $12.0 | $9.00 |
| Accepts | text, audio, files, images, video | text, audio, files, images, video |
| Produces | text | text |
| Reasoning | Yes | Yes |
| Tool use | Yes | Yes |
| Added to OpenRouter | 2026-02-19 | 2026-05-19 |
| Model ID | google/gemini-3.1-pro-preview | google/gemini-3.5-flash |
Questions and answers
Which is cheaper, Gemini 3.1 Pro Preview or Gemini 3.5 Flash?
Gemini 3.5 Flash costs less for both input ($1.50 vs $2.00) and output ($9.00 vs $12.0) per million tokens. On input, Gemini 3.5 Flash is 25% cheaper.
Which has the larger context window?
Both have a 1.05M-token context window.
What can one do that the other cannot?
Nothing among reasoning, tool use and image input: both support reasoning, tool use and image input.
Answers are computed from the 2026-10-24 catalog snapshot.