> ## Documentation Index
> Fetch the complete documentation index at: https://docs.galileo.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Dataset validation

> Schema and content checks Luna Studio runs on every dataset, and how to fix common errors.

Every dataset added to Luna Studio — uploaded, fetched, generated, or imported — goes through validation. Validation determines whether the dataset can be used in a run.

## What Luna Studio checks

### Schema checks

* The file parses as CSV or JSONL.
* Required columns are present:
  * **Test sets** — metric-specific feature columns and `label`.
  * **Training sets** — metric-specific feature columns and optionally `label` when applicable.
* Column types match the metric's [output type](/luna-studio/ui/core-concepts#metrics) (e.g. labels are parseable as Boolean for a Boolean metric).

### Content checks

* File encoding (UTF-8 expected).
* Row count > 0.
* Empty rows or empty cells

### File checks (uploads and URLs)

* File size within the upload limit.
* For URLs: the URL is reachable; the response content type is appropriate.

## Common errors

| Error message                                  | Cause                                                                 | Fix                                                                                                           |
| ---------------------------------------------- | --------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------- |
| `Missing column "label" in uploaded CSV.`      | Test set or labelled training set without a `label` column.           | Add the column to your file and re-upload. For unlabelled training logs, use the label-only flow from Step 3. |
| `Missing column "input" in uploaded CSV.`      | Required `input` column missing.                                      | Rename your input column to `input`, or include one.                                                          |
| `Could not fetch URL.`                         | The URL was unreachable, returned a non-2xx status, or required auth. | Check the URL is correct; for cloud URLs, confirm the relevant integration has access.                        |
| `Unsupported file type.`                       | The file isn't `.csv` or `.jsonl`.                                    | Convert the file to one of the supported formats.                                                             |
| `Empty dataset.`                               | The file parsed but had zero data rows.                               | Confirm the file isn't header-only.                                                                           |
| `Label values don't match metric output type.` | Labels can't be parsed as the metric's expected type.                 | Re-check labels (e.g. for Boolean: only `true`/`false` or `1`/`0`).                                           |

## Where to go next

<CardGroup cols={2}>
  <Card title="Add a dataset" icon="upload" href="/luna-studio/ui/datasets/add-a-dataset">
    Walk through the three sources.
  </Card>

  <Card title="Troubleshooting" icon="bug" href="/luna-studio/ui/reference/troubleshooting">
    Run-time failures and how to recover.
  </Card>
</CardGroup>