Gemini 3.1 Pro Preview vs GPT-5.5 Instant
Gemini 3.1 Pro Preview (2026) and GPT-5.5 Instant (2026) are general-purpose language models from Google DeepMind and OpenAI. Gemini 3.1 Pro Preview ships a 1m-token context window, while GPT-5.5 Instant ships a 400k-token context window. On MMMU Pro, Gemini 3.1 Pro Preview leads by 12.2 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
GPT-5.5 Instant is safer overall; choose Gemini 3.1 Pro Preview when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview | GPT-5.5 Instant |
|---|---|---|
| Best for | multimodal apps, tool-calling agents, and long-context analysis | multimodal apps and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 400k |
| Cheapest output | $12/1M tokens | $30/1M tokens |
| Provider routes | 5 tracked | 1 tracked |
| Shared benchmarks | MMMU Pro leader | 1 shared |
Decision tradeoffs
- Gemini 3.1 Pro Preview holds a shared-benchmark lead on MMMU Pro, ahead by 12.2 points.
- Gemini 3.1 Pro Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3.1 Pro Preview has the lower cheapest tracked output price at $12/1M tokens.
- Gemini 3.1 Pro Preview has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Gemini 3.1 Pro Preview for Coding, RAG, and Agents.
- Local decision data tags GPT-5.5 Instant 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 Pro Preview
$4,600
Cheapest tracked route/tier: Google AI Studio
GPT-5.5 Instant
$11,500
Cheapest tracked route/tier: OpenAI API
Estimated monthly gap: $6,900. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 3.1 Pro Preview and GPT-5.5 Instant; plan for SDK, billing, or endpoint changes.
- GPT-5.5 Instant is $18/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- No overlapping tracked provider route is sourced for GPT-5.5 Instant and Gemini 3.1 Pro Preview; plan for SDK, billing, or endpoint changes.
- Gemini 3.1 Pro Preview is $18/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-19 | 2026-05-05 |
| Context window | 1m | 400k |
| 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 Pro Preview | GPT-5.5 Instant |
|---|---|---|
| Input price |
| $5/1M tokens |
| Output price |
| $30/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview | GPT-5.5 Instant |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | No |
| 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 Pro Preview | GPT-5.5 Instant |
|---|---|---|
| MMMU Pro | 88.2 | 76.0 |
Deep dive
On shared benchmark coverage, MMMU Pro has Gemini 3.1 Pro Preview at 88.2 and GPT-5.5 Instant at 76, with Gemini 3.1 Pro Preview ahead by 12.2 points. The largest visible gap is 12.2 points on MMMU Pro, 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 is close: both models cover vision, multimodal input, function calling, tool use, and structured outputs. That makes context budget, benchmark fit, and provider maturity more important than a simple checklist. If your application depends on one integration detail, verify it against the provider route you plan to use, not just the base model listing.
For cost, Gemini 3.1 Pro Preview lists tiered pricing: 0-200,001t is $2/1M input and $12/1M output; 200,001t+ is $4/1M input and $18/1M output, while GPT-5.5 Instant lists $5/1M input and $30/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Gemini 3.1 Pro Preview lower by about $7.50 per million blended tokens. For tiered rows, this cheapest-track view can understate interactive or fast-lane spend, so compare the tier you will actually use. Availability is 5 providers versus 1, so concentration risk also matters.
Choose Gemini 3.1 Pro Preview when coding workflow support, larger context windows, and lower cheapest-tier input-token cost are central to the workload. Choose GPT-5.5 Instant 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 Pro Preview or GPT-5.5 Instant?
Gemini 3.1 Pro Preview supports 1m tokens, while GPT-5.5 Instant supports 400k 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 Pro Preview or GPT-5.5 Instant?
Gemini 3.1 Pro Preview lists tiered pricing: 0-200,001t is $2/1M input and $12/1M output; 200,001t+ is $4/1M input and $18/1M output. GPT-5.5 Instant lists $5/1M input and $30/1M output tokens on the cheapest tracked provider. Compare the tier you will actually use; cheap async pricing can overstate savings for interactive workflows. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Pro Preview or GPT-5.5 Instant open source?
Gemini 3.1 Pro Preview is listed under Proprietary. GPT-5.5 Instant 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 Pro Preview or GPT-5.5 Instant?
Both Gemini 3.1 Pro Preview and GPT-5.5 Instant 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 Pro Preview or GPT-5.5 Instant?
Both Gemini 3.1 Pro Preview and GPT-5.5 Instant 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 Pro Preview and GPT-5.5 Instant?
Gemini 3.1 Pro Preview is available on Google AI Studio, GCP Vertex AI, OpenRouter, Replicate API, and Vercel AI Gateway. GPT-5.5 Instant is available on OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.