Gemini 3.5 Flash vs Grok 4
Gemini 3.5 Flash (2026) and Grok 4 (2025) are frontier-tier reasoning models from Google DeepMind and xAI. Gemini 3.5 Flash ships a 1M-token context window, while Grok 4 ships a 256k-token context window. On pricing, Grok 4 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. It focuses on practical selection signals rather than broad model-family marketing.
Gemini 3.5 Flash fits 4x more tokens; pick it for long-context work and Grok 4 for tighter calls.
Decision scorecard
Local evidence first| Signal | Gemini 3.5 Flash | Grok 4 |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 256k |
| Cheapest output | $9/1M tokens | $2.5/1M tokens |
| Provider routes | 2 tracked | 4 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Gemini 3.5 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Local decision data tags Gemini 3.5 Flash for Coding, RAG, and Agents.
- Grok 4 has the lower cheapest tracked output price at $2.5/1M tokens.
- Grok 4 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Grok 4 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Gemini 3.5 Flash
$3,450
Cheapest tracked route: Google AI Studio
Grok 4
$1,625
Cheapest tracked route: xAI Console
Estimated monthly gap: $1,825. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 3.5 Flash and Grok 4; plan for SDK, billing, or endpoint changes.
- Grok 4 is $6.5/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- No overlapping tracked provider route is sourced for Grok 4 and Gemini 3.5 Flash; plan for SDK, billing, or endpoint changes.
- Gemini 3.5 Flash is $6.5/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-19 | 2025-07-09 |
| Context window | 1M | 256k |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-01 | - |
Pricing and availability
| Pricing attribute | Gemini 3.5 Flash | Grok 4 |
|---|---|---|
| Input price | $1.5/1M tokens | $1.25/1M tokens |
| Output price | $9/1M tokens | $2.5/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.5 Flash | Grok 4 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint is close: both models cover vision, multimodal input, reasoning mode, function calling, and tool use. 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 3.5 Flash lists $1.5/1M input and $9/1M output tokens, while Grok 4 lists $1.25/1M input and $2.5/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Grok 4 lower by about $2.12 per million blended tokens. Availability is 2 providers versus 4, so concentration risk also matters.
Choose Gemini 3.5 Flash when coding workflow support and larger context windows are central to the workload. Choose Grok 4 when coding workflow support, lower input-token cost, 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. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, Gemini 3.5 Flash or Grok 4?
Gemini 3.5 Flash supports 1M tokens, while Grok 4 supports 256k 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 3.5 Flash or Grok 4?
Grok 4 is cheaper on tracked token pricing. Gemini 3.5 Flash costs $1.5/1M input and $9/1M output tokens. Grok 4 costs $1.25/1M input and $2.5/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.5 Flash or Grok 4 open source?
Gemini 3.5 Flash is listed under Proprietary. Grok 4 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 3.5 Flash or Grok 4?
Both Gemini 3.5 Flash and Grok 4 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Gemini 3.5 Flash or Grok 4?
Both Gemini 3.5 Flash and Grok 4 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 3.5 Flash and Grok 4?
Gemini 3.5 Flash is available on Google AI Studio and GCP Vertex AI. Grok 4 is available on Microsoft Foundry, OpenRouter, Replicate API, and xAI Console. 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.