Page-Speed normally refers to the time it takes for a web-page to be presented to a browser in a "fully loaded" state.
Page-Speed of a web-page can be broken down into several distinct aspects:
- Initial Request - comprising of the DNS request, the socket connection and the transmitting of the first byte
- Start Render - when a first non-white element is introduced to the page, often referred to as the start of page "paint"
- Document Complete - when the core elements of the page are loaded so that user interaction can be performed
- Fully Loaded - when every element requested has been loaded and presented - no more data is requested and all painting has been finalized.
Measuring of page-speed can be a complex task as there are many variables at play, and small intricacies such as the number and loading order of requests, asynchronous requests, compression, caching and so on all have an impact.
While Page-Speed has been a User Experience (UX) issue for some time, it was recently announced as a factor in Google's ranking algorithm which has spurred greater interest and focus on the topic.