Gemini 3.1 Flash Lite Preview vs o3-pro
Gemini 3.1 Flash Lite Preview (2026) and o3-pro (2025) are frontier reasoning models from Google DeepMind and OpenAI. Gemini 3.1 Flash Lite Preview ships a 1m-token context window, while o3-pro ships a 200k-token context window. On Google-Proof Q&A, Gemini 3.1 Flash Lite Preview leads by 2.9 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Gemini 3.1 Flash Lite Preview is ~7900% cheaper at $0.25/1M; pay for o3-pro only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Flash Lite Preview | o3-pro |
|---|---|---|
| Best for | multimodal apps, tool-calling agents, and long-context analysis | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 200k |
| Cheapest output | $1.50/1M tokens | $80/1M tokens |
| Provider routes | 4 tracked | 3 tracked |
| Shared benchmarks | Google-Proof Q&A leader | 1 shared |
Decision tradeoffs
- Gemini 3.1 Flash Lite Preview holds a shared-benchmark lead on Google-Proof Q&A, ahead by 2.9 points.
- Gemini 3.1 Flash Lite Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3.1 Flash Lite Preview has the lower cheapest tracked output price at $1.50/1M tokens.
- Gemini 3.1 Flash Lite Preview has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Gemini 3.1 Flash Lite Preview for Coding, RAG, and Agents.
- o3-pro uniquely exposes Reasoning in local model data.
- Local decision data tags o3-pro for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Gemini 3.1 Flash Lite Preview
$575
Cheapest tracked route/tier: Google AI Studio
o3-pro
$36,000
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $35,425. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- o3-pro is $78.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- o3-pro adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- Gemini 3.1 Flash Lite Preview is $78.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-03-03 | 2025-06-10 |
| Context window | 1m | 200k |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-01 | 2025-08 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Flash Lite Preview | o3-pro |
|---|---|---|
| Input price | $0.25/1M tokens | $20/1M tokens |
| Output price | $1.50/1M tokens | $80/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Flash Lite Preview | o3-pro |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Gemini 3.1 Flash Lite Preview | o3-pro |
|---|---|---|
| Google-Proof Q&A | 86.9 | 84.0 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has Gemini 3.1 Flash Lite Preview at 86.9 and o3-pro at 84, with Gemini 3.1 Flash Lite Preview ahead by 2.9 points. The largest visible gap is 2.9 points on Google-Proof Q&A, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on reasoning mode: o3-pro. Both models share vision, multimodal input, function calling, and tool use, 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 3.1 Flash Lite Preview lists $0.25/1M input and $1.50/1M output tokens on the cheapest tracked provider, while o3-pro lists $20/1M input and $80/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Gemini 3.1 Flash Lite Preview lower by about $37.38 per million blended tokens. Availability is 4 providers versus 3, so concentration risk also matters.
Choose Gemini 3.1 Flash Lite Preview when coding workflow support, larger context windows, and lower input-token cost are central to the workload. Choose o3-pro when coding workflow support 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 3.1 Flash Lite Preview or o3-pro?
Gemini 3.1 Flash Lite Preview supports 1m tokens, while o3-pro supports 200k 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 3.1 Flash Lite Preview or o3-pro?
Gemini 3.1 Flash Lite Preview is cheaper on tracked token pricing. Gemini 3.1 Flash Lite Preview costs $0.25/1M input and $1.50/1M output tokens. o3-pro costs $20/1M input and $80/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Flash Lite Preview or o3-pro open source?
Gemini 3.1 Flash Lite Preview is listed under Proprietary. o3-pro 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 3.1 Flash Lite Preview or o3-pro?
Both Gemini 3.1 Flash Lite Preview and o3-pro expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, Gemini 3.1 Flash Lite Preview or o3-pro?
Both Gemini 3.1 Flash Lite Preview and o3-pro expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run Gemini 3.1 Flash Lite Preview and o3-pro?
Gemini 3.1 Flash Lite Preview is available on Google AI Studio, GCP Vertex AI, OpenRouter, and Vercel AI Gateway. o3-pro is available on OpenRouter, OpenAI API, and Vercel AI Gateway. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-06-15. Data sourced from public model cards and provider documentation.