---
name: dt-js-runtime
description: Dynatrace server-side JS runtime — function contract, runtime limits, Web APIs, Node.js modules, fetch with credential vault, and the @dynatrace-sdk/* catalog.
license: Apache-2.0
---
# Dynatrace JavaScript Runtime
The Dynatrace JS runtime is a server-side AppEngine sandbox that executes JavaScript/TypeScript.
## Function contract
Every entry point must export a default async function:
```js
export default async function () {
// ...
return result;
}
```
ES module syntax required. TypeScript accepted (type annotations, interfaces, generics). No other export shape is supported.
## References
Start here, then load only the file you need.
| File | When to load |
|------|-------------|
| [references/limits-and-restrictions.md](references/limits-and-restrictions.md) | Timeout / memory / I/O quotas; what's forbidden (`eval`, WebSocket, sockets, filesystem) |
| [references/apis-and-modules.md](references/apis-and-modules.md) | Which Web APIs and Node.js compat modules are available (fetch, crypto, streams, buffer, …) |
| [references/fetch.md](references/fetch.md) | Calling internal `/platform/...` APIs or external URLs, credential vault, outbound allowlist |
| [references/sdk.md](references/sdk.md) | Any `@dynatrace-sdk/*` package — the index routes you to the right per-SDK file |
## Running a function with dtctl
Use `dtctl exec function` to run JS runtime code without deploying an app.
```dtctl
# Run inline code
dtctl exec function --code 'export default async function() { return "hello" }'
# Run from file
dtctl exec function -f script.js
# Pass JSON input — accessed as event.payload inside the function
dtctl exec function -f script.js --payload '{"key":"value"}'
```
The function may accept an optional `event` parameter:
```js
export default async function(event) {
const { payload } = event; // from --payload
// event.environmentId also available
return payload;
}
```
Load the **`dynatrace-control`** skill for authentication setup, context switching, and the full `exec function` reference.