Gemini 2.5 Pro Preview 05-06 vs Gemini 3.5 Flash
Gemini 2.5 Pro Preview 05-06 (2025) and Gemini 3.5 Flash (2026) are frontier reasoning models from Google DeepMind. Gemini 2.5 Pro Preview 05-06 ships a 1M-token context window, while Gemini 3.5 Flash ships a 1M-token context window. On pricing, Gemini 2.5 Pro Preview 05-06 costs $1.25/1M input tokens versus $1.5/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Gemini 3.5 Flash is safer overall; choose Gemini 2.5 Pro Preview 05-06 when provider fit matters.
Decision scorecard
Local evidence first| Signal | Gemini 2.5 Pro Preview 05-06 | Gemini 3.5 Flash |
|---|---|---|
| Decision fit | RAG, Long context, and Vision | Coding, RAG, and Agents |
| Context window | 1M | 1M |
| Cheapest output | $10/1M tokens | $9/1M tokens |
| Provider routes | 1 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Local decision data tags Gemini 2.5 Pro Preview 05-06 for RAG, Long context, and Vision.
- Gemini 3.5 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3.5 Flash has the lower cheapest tracked output price at $9/1M tokens.
- Gemini 3.5 Flash has broader tracked provider coverage for fallback and procurement flexibility.
- Gemini 3.5 Flash uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags Gemini 3.5 Flash for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Gemini 2.5 Pro Preview 05-06
$3,500
Cheapest tracked route: OpenRouter
Gemini 3.5 Flash
$3,450
Cheapest tracked route: Google AI Studio
Estimated monthly gap: $50.00. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 2.5 Pro Preview 05-06 and Gemini 3.5 Flash; plan for SDK, billing, or endpoint changes.
- Gemini 3.5 Flash is $1/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Gemini 3.5 Flash adds Vision, Multimodal, and Reasoning in local capability data.
- No overlapping tracked provider route is sourced for Gemini 3.5 Flash and Gemini 2.5 Pro Preview 05-06; plan for SDK, billing, or endpoint changes.
- Gemini 2.5 Pro Preview 05-06 is $1/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-05-06 | 2026-05-19 |
| Context window | 1M | 1M |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Unknown | Proprietary |
| Knowledge cutoff | 2025-01 | 2025-01 |
Pricing and availability
| Pricing attribute | Gemini 2.5 Pro Preview 05-06 | Gemini 3.5 Flash |
|---|---|---|
| Input price | $1.25/1M tokens | $1.5/1M tokens |
| Output price | $10/1M tokens | $9/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 2.5 Pro Preview 05-06 | Gemini 3.5 Flash |
|---|---|---|
| Vision | No | Yes |
| Multimodal | No | Yes |
| Reasoning | No | Yes |
| Function calling | No | Yes |
| Tool use | No | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | Yes |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: Gemini 3.5 Flash, multimodal input: Gemini 3.5 Flash, reasoning mode: Gemini 3.5 Flash, function calling: Gemini 3.5 Flash, tool use: Gemini 3.5 Flash, and code execution: Gemini 3.5 Flash. Both models share structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Gemini 2.5 Pro Preview 05-06 lists $1.25/1M input and $10/1M output tokens, while Gemini 3.5 Flash lists $1.5/1M input and $9/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Gemini 3.5 Flash lower by about $0.13 per million blended tokens. Availability is 1 providers versus 2, so concentration risk also matters.
Choose Gemini 2.5 Pro Preview 05-06 when provider fit and lower input-token cost are central to the workload. Choose Gemini 3.5 Flash when coding workflow support, larger context windows, and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Gemini 2.5 Pro Preview 05-06 or Gemini 3.5 Flash?
Gemini 3.5 Flash supports 1M tokens, while Gemini 2.5 Pro Preview 05-06 supports 1M tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Gemini 2.5 Pro Preview 05-06 or Gemini 3.5 Flash?
Gemini 2.5 Pro Preview 05-06 is cheaper on tracked token pricing. Gemini 2.5 Pro Preview 05-06 costs $1.25/1M input and $10/1M output tokens. Gemini 3.5 Flash costs $1.5/1M input and $9/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 2.5 Pro Preview 05-06 or Gemini 3.5 Flash open source?
Gemini 2.5 Pro Preview 05-06 is listed under Unknown. Gemini 3.5 Flash is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Gemini 2.5 Pro Preview 05-06 or Gemini 3.5 Flash?
Gemini 3.5 Flash has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for multimodal input, Gemini 2.5 Pro Preview 05-06 or Gemini 3.5 Flash?
Gemini 3.5 Flash has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Gemini 2.5 Pro Preview 05-06 and Gemini 3.5 Flash?
Gemini 2.5 Pro Preview 05-06 is available on OpenRouter. Gemini 3.5 Flash is available on Google AI Studio and GCP Vertex AI. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-19. Data sourced from public model cards and provider documentation.