--- title: "Assets Module" url: https://develop.sentry.dev/sdk/telemetry/traces/modules/assets/ --- # Assets Module Browser SDKs should auto-instrument javascript, stylesheet and image assets with the ops `resource.script`, `resource.css` and `resource.img` respectively. The Asset module is technology agnostic, it only cares about span data properties. ## [Span conventions](https://develop.sentry.dev/sdk/telemetry/traces/modules/assets.md#span-conventions) ### [Span Description](https://develop.sentry.dev/sdk/telemetry/traces/modules/assets.md#span-description) The description of an asset span should be the full URL of the asset, e.g., `https://cdn.com/main.hash123.js?q=11274713`. ### [Span Data](https://develop.sentry.dev/sdk/telemetry/traces/modules/assets.md#span-data) The following data should be provided for each asset span | Data Key | Type | Description | Notes | | -------------------------------------- | -------- | --------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- | | `http.response_content_length` | `int` | encoded size of the asset in `bytes` (what is sent over the network) | required on all asset operations | | `http.decoded_response_content_length` | `int` | the decoded size of the asset in `bytes` | recommended; if not provided, would show up as 0 on the resource summary size chart | | `http.response_transfer_size` | `int` | the size of the encoded asset plus the response headers in `bytes` | recommended; if not provided, would show up as 0 on the resource summary size chart | | `resource.render_blocking_status` | `string` | whether the resource blocks UI rendering, values are 'non-blocking' or 'blocking' | recommended; if not provided, the asset can't be narrowed down by their render blocking status | ## [Instrumentation Example](https://develop.sentry.dev/sdk/telemetry/traces/modules/assets.md#instrumentation-example) The SDK should create a span per asset fetched by the browser. Consider a basic HTML file that fetches a single script: ```html ``` Should result in the following span, assuming the request was successful: ```json { "description": "https://cdn.com/main.hash123.js", "op": "resource.script", "data": { "http.decoded_response_content_length": 123, "http.response_content_length": 123, "http.response_transfer_size": 123, "resource.render_blocking_status": "blocking", "server.address": "cdn.com", ... other span properties } } ```