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

# Get the preview

> Read the latest generated preview — the proposed output, sheet-per-template — so your customer can review it before you execute.

```http theme={null}
GET https://app.vern.so/api/v1/migrations/{migration_id}/preview
```

Returns the **current preview** — the output of the latest
[`generate` or `update` run](/migration-api/start-a-run), mapped to your templates
sheet-by-sheet. This is exactly what the agent proposes to import; show it to your
customer, then refine or [execute](/migration-api/start-a-run).

A migration has a preview once a `generate`/`update` run reaches
`awaiting_approval`. Before that, this returns `404`.

## Authentication

Requires an `x-api-key` header. See [Authentication](/migration-api/authentication).

## Response

`200 OK`

```json theme={null}
{
  "status": "awaiting_approval",
  "templates": [
    { "slug": "contacts", "name": "Contacts" }
  ],
  "sheets": [
    {
      "template": { "slug": "contacts", "name": "Contacts" },
      "rows": [
        ["Email", "First Name", "Last Name", "Account"],
        ["jane@acme.com", "Jane", "Doe", "Acme Corp"],
        ["john@acme.com", "John", "Smith", "Acme Corp"]
      ],
      "invalid_cells": []
    }
  ]
}
```

<ResponseField name="status" type="string">
  Always `awaiting_approval` when a preview exists.
</ResponseField>

<ResponseField name="templates" type="object[]">
  The templates this migration targets, each `{ slug, name }`.
</ResponseField>

<ResponseField name="sheets" type="object[]">
  One entry per output sheet:

  <Expandable title="sheet">
    <ResponseField name="template" type="object">
      `{ slug, name }` — the template this sheet maps to.
    </ResponseField>

    <ResponseField name="rows" type="string[][]">
      The proposed rows as a grid, header row first.
    </ResponseField>

    <ResponseField name="invalid_cells" type="object[]">
      Cells flagged invalid in the preview. Empty in the common case.
    </ResponseField>
  </Expandable>
</ResponseField>

## Errors

| Status | Meaning                                                           |
| ------ | ----------------------------------------------------------------- |
| `401`  | API key missing or invalid.                                       |
| `404`  | No preview generated yet, or the migration isn't in your account. |
| `429`  | Rate limit hit — back off and retry.                              |
| `500`  | Server error.                                                     |

## Example

```bash theme={null}
curl https://app.vern.so/api/v1/migrations/c0a8012e-.../preview \
  -H "x-api-key: $VERN_API_KEY"
```

## Next

* [Start a run](/migration-api/start-a-run) — `update` to refine, or `execute` to import.
* [Export CSV](/migration-api/export-csv) — get the validated rows after execute.