gemini 3.1 flash lite preview is Google's low-cost, high-throughput entry in the 3.1 lineup — the model you reach for when you're running thousands of calls a day and can't afford Pro pricing on every one of them. It still reasons, still calls functions, still reads images and video, but it's tuned for volume over depth. Teams doing document triage, multimodal classification, or lightweight agent steps are the ones who benefit most.
Context window and what it costs
The context window is 1,048,576 tokens with up to 65,536 tokens of output per call, so a single request can hold a long transcript, a stack of PDFs, or hours of chat history without chunking. Pricing is $0.25 per million input tokens and $1.50 per million output tokens, and cached input drops to $0.025 per million — a 10x discount on tokens you send repeatedly, like a system prompt or a reference document that doesn't change between calls. For a support bot that re-sends a 40-page policy doc on every turn, caching alone can cut the bill by more than half.
Where it actually earns its keep
- Bulk PDF and document extraction where the alternative is a chunking pipeline
- Multimodal triage across text, image, video, audio, and PDF inputs in one call
- Agent steps that need function calling but not deep multi-hop reasoning
- High-volume classification and tagging jobs billed per call, not per cleverness
How it stacks up against the rest of the 3.1 line
Gemini 3.1 Pro Preview costs $2.00 per million input tokens and $12.00 per million output — eight times the input price and eight times the output price of Flash Lite. What's notable is the capability score gap doesn't match the price gap: Flash Lite Preview sits at 88.6, actually a hair above Pro Preview's 88.5. That doesn't mean Flash Lite is the smarter model for every task; capability scores compress a lot of nuance and Pro likely wins on harder multi-step reasoning. But it does mean Flash Lite deserves a real trial before defaulting to Pro for anything short of your hardest problems.
The honest limitation
This is a preview release, which means Google can still change pricing, rate limits, or behavior before it graduates to general availability — don't build a production SLA around it without a fallback plan. Output is text only; there's no native image or audio generation, so pipelines that need generated media alongside the response still need a second model in the loop.