---
title: setDefaultDynamicBackendConfig
summary: Set the default backend configuration options for dynamic backends.
url: https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/backend/fn.setDefaultDynamicBackendConfig/
---

**Kind:** Function  
**Module:** [backend](https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/backend/)  
**Package:** @fastly/js-compute 4.0.1  
**Since:** 3.24.0  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/backend.d.ts#L38

```javascript
setDefaultDynamicBackendConfig(defaultDynamicBackendConfiguration: DefaultBackendConfiguration): void
```

Set the default backend configuration options for dynamic backends.

Applies to backends created via [new Backend(...)](https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/backend/class.Backend/) as well as for dynamic backends
implicitly created when using [fetch()](https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/globals/fn.fetch/).

**Parameters**

- `defaultDynamicBackendConfiguration`: `DefaultBackendConfiguration` — default backend configuration options

**Returns**

`void`

````javascript
Setting default timeouts and TLS options for all newly created dynamic backends:
```js
import { Backend, setDefaultDynamicBackendConfig } from "fastly:backend";
setDefaultDynamicBackendConfig({
  connectTimeout: 1000,          // milliseconds
  firstByteTimeout: 15_000,      // milliseconds
  betweenBytesTimeout: 10_000,   // milliseconds
  useSSL: true,
  tlsMinVersion: 1.3,
  tlsMaxVersion: 1.3,
});
// Timeouts and TLS configuration are inherited from the defaults above.
const backend = new Backend({
  target: 'my-site.com',
  hostOverride: "www.my-site.com",
});
```
````