Device Pixel Ratio (DPR)
The Device Pixel Ratio indicates the density of pixels on a device's screen. High-resolution displays (like Apple's "Retina" screens) have a DPR of 2 or more, meaning they use a 2x2 grid of physical pixels to render what is a single CSS pixel. This is important for Image Optimization, as you should serve higher-resolution images to these devices for sharpness, but not images that are so large they waste bandwidth and slow down loading.
Related web performance terms
- DOM (Document Object Model)
The DOM is a tree-like representation of all the elements in an HTML document that is created by the browser when it loads a page.
- DOM Content Loaded
DOM Content Loaded (DOMContentLoaded or DCL) is a browser event that fires when the initial HTML document has been completely loaded and parsed, without waiting for stylesheets, images, and subframes to finish loading.
- DOM Size
DOM Size refers to the total number of elements (nodes) and the complexity of their nesting within a page's HTML structure.
- Deferred JS loading
Deferred JS loading is a technique for loading JavaScript files in a non-blocking way using the `defer` attribute on a `<script>` tag.