# Datasets

The **Datasets** section is where you upload and manage the data your training jobs run on. It mirrors `client.datasets` in the [SDK](/docs/sdk).

## Upload a dataset

Click **Upload dataset** and select a local `.jsonl` file. Fleet uploads it to object storage and lists it with its name, size, and upload time.

Datasets are content-hashed, so uploading the same file twice doesn't duplicate storage.

## Dataset format

Training expects newline-delimited JSON (`.jsonl`), one example per line. The exact schema depends on your training method; for chat-style fine-tuning each line is typically a conversation with a `messages` array. See [Training](/docs/training) for method-specific details.

## Using a dataset

When you start a training job from the [Models](/docs/dashboard-models) section, your uploaded datasets appear in the dataset picker. Selecting one also unlocks the live cost and time **estimate** for the run, since Fleet uses the dataset's row count to project how long training will take.

## Manage datasets

Each row offers a delete action. Datasets are billed as stored data while they exist; deleting one frees its storage immediately. See [Storage](/docs/storage) for how storage is metered.