Header Snippets are small pieces of JavaScript code that can be injected into a Page's HTML so that even before Boomerang loads, components of the page load experience (such as JavaScript errors) are still fully measured.
These Header Snippets should be added as inline `
```
Minified:
```javascript
```
## Frame Rate (for {@link BOOMR.plugins.Continuity})
The {@link BOOMR.plugins.Continuity} plugin measures performance and user experience metrics beyond just the
traditional Page Load timings.
One of the metrics that the {@link BOOMR.plugins.Continuity} plugin measures is Frame Rate (FSP) data via
[`requestAnimationFrame`](https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame). However,
FPS data is "real-time" and is not available for scripts like Boomerang that may load later in the page load process.
This Header Snippet will start monitoring
[`requestAnimationFrame`](https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame) and hand the
FPS data off to Boomerang once it has loaded.
Source:
```javascript
```
Minified:
```javascript
```
## Instrumenting XMLHttpRequests (for {@link BOOMR.plugins.AutoXHR})
The {@link BOOMR.plugins.AutoXHR} plugin monitors `XMLHttpRequests` on the page.
The performance data of `XMLHttpRequests` that start before Boomerang is loaded may not be monitored.
This Header Snippet will start monitoring `XMLHttpRequests` and hand the performance data off to Boomerang once it
has loaded.
Source:
```javascript
```
Minified:
```javascript
```