---
title: "Run a sample submission through a source's mapping"
method: POST
path: "/v1/streams/{streamId}/preview"
tags: ["streams"]
---

# Run a sample submission through a source's mapping

`POST /v1/streams/{streamId}/preview`

## Request

- Base URL: `https://postbag.dev`
- URL: `https://postbag.dev/v1/streams/{streamId}/preview`
- Auth: HTTP bearer

Dry-runs a form's attached mapping against sample data without storing anything — useful before publishing a schema change.

## Path parameters

- `streamId` string, required

## Request body

- object
  - `form_id` string, required: The form whose attached mapping to run.
  - `data` object, required: Sample submission data to map through.

## Response `200`

ok

- object
  - `payload` object, required
  - `extras` object, required
  - `problems` string[], required

---

[API](https://skmtc.dev/postbag/apis/postbag-api.md) · [All operations](https://skmtc.dev/postbag/apis/postbag-api/llms.txt) · [OpenAPI document](https://skmtc.dev/postbag/apis/postbag-api/revisions/3da976524695?raw)