---
title: "Get a thumbnail image from a block's video tap."
method: GET
path: "/api/flows/{id}/blocks/{block_id}/thumbnail"
tags: ["flows"]
---

# Get a thumbnail image from a block's video tap.

`GET /api/flows/{id}/blocks/{block_id}/thumbnail`

Works with any block that exposes thumbnail tee elements, including
`builtin.thumbnail` (index 0) and compositor blocks (one per input).
The first request activates the thumbnail branch; subsequent requests
are served from cache.

## Path parameters

- `id` string, required
- `block_id` string, required

## Query parameters

- `index` integer

## Response `200`

JPEG thumbnail image

## Other responses

- `404` — Flow not running or block not found
- `504` — Frame capture timed out (retry shortly)

---

[API](https://skmtc.dev/eyevinn/apis/strom-api.md) · [All operations](https://skmtc.dev/eyevinn/apis/strom-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/eyevinn/strom-api/revisions/0df7ca64263f/schema)