LLM Reference

Gemini 2.5 Pro vs Gemini 3.1 Pro Preview

Gemini 2.5 Pro (2025) and Gemini 3.1 Pro Preview (2026) are frontier reasoning models from Google DeepMind. Gemini 2.5 Pro ships a 1m-token context window, while Gemini 3.1 Pro Preview ships a 1m-token context window. On MMLU PRO, Gemini 3.1 Pro Preview leads by 4.8 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 Pro Preview is safer overall; choose Gemini 2.5 Pro when coding workflow support matters.

Decision scorecard

Local evidence first
SignalGemini 2.5 ProGemini 3.1 Pro Preview
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentsmultimodal apps, tool-calling agents, and long-context analysis
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window1m1m
Cheapest output$10/1M tokens$12/1M tokens
Provider routes4 tracked5 tracked
Shared benchmarks8 sharedMMLU PRO leader

Decision tradeoffs

Choose Gemini 2.5 Pro when...
  • Gemini 2.5 Pro has the lower cheapest tracked output price at $10/1M tokens.
  • Gemini 2.5 Pro uniquely exposes Reasoning in local model data.
  • Local decision data tags Gemini 2.5 Pro for Coding, RAG, and Agents.
Choose Gemini 3.1 Pro Preview when...
  • Gemini 3.1 Pro Preview holds a shared-benchmark lead on MMLU PRO, ahead by 4.8 points.
  • Gemini 3.1 Pro Preview has broader tracked provider coverage for fallback and route flexibility.
  • Local decision data tags Gemini 3.1 Pro Preview 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.

Lower estimate Gemini 2.5 Pro

Gemini 2.5 Pro

$3,500

Cheapest tracked route/tier: Google AI Studio <=200K tokens

Gemini 3.1 Pro Preview

$4,600

Cheapest tracked route/tier: Google AI Studio

Estimated monthly gap: $1,100. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Gemini 2.5 Pro -> Gemini 3.1 Pro Preview
  • Provider overlap exists on Google AI Studio, GCP Vertex AI, and OpenRouter; start route-level A/B tests there.
  • Gemini 3.1 Pro Preview is $2/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Check replacement coverage for Reasoning before moving production traffic.
Gemini 3.1 Pro Preview -> Gemini 2.5 Pro
  • Provider overlap exists on Google AI Studio, GCP Vertex AI, and OpenRouter; start route-level A/B tests there.
  • Gemini 2.5 Pro is $2/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Gemini 2.5 Pro adds Reasoning in local capability data.

Specs

Specification
Released2025-06-172026-02-19
Context window1m1m
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-012025-01

Pricing and availability

Pricing attributeGemini 2.5 ProGemini 3.1 Pro Preview
Input price
<=200K tokens
$1.25/1M tokens
Standard Gemini 2.5 Pro pricing for prompts up to 200K tokens.
>200K tokens
$2.50/1M tokens
Higher Gemini 2.5 Pro tier for prompts above 200K tokens.
0-200,001t
$2/1M tokens
200,001t+
$4/1M tokens
Output price
<=200K tokens
$10/1M tokens
Standard Gemini 2.5 Pro pricing for prompts up to 200K tokens.
>200K tokens
$15/1M tokens
Higher Gemini 2.5 Pro tier for prompts above 200K tokens.
0-200,001t
$12/1M tokens
200,001t+
$18/1M tokens
Providers
Google AI StudioGCP Vertex AIOpenRouterVercel AI Gateway
Google AI StudioGCP Vertex AIOpenRouterReplicate APIVercel AI Gateway

Capabilities

CapabilityGemini 2.5 ProGemini 3.1 Pro Preview
VisionYesYes
MultimodalYesYes
ReasoningYesNo
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkGemini 2.5 ProGemini 3.1 Pro Preview
MMLU PRO86.291.0
SWE-bench Verified63.880.6
Google-Proof Q&A86.494.3
AIME 202586.795.0
LiveCodeBench75.691.7
Humanity's Last Exam18.851.4
HumanEval93.194.0
Chatbot Arena1398.01493.0

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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.