From Server to Screen
- The file is downloaded from a server. How long this takes depends on the size of the file, and the speed of your network.
- The file is decompressed and parsed, so the browser knows what it contains.
In exchange, they frequently find themselves shipping code that is actively user-hostile or exploitative. While these are extreme cases, it's vital to monitor the effect any third-party scripts are having on your site. In more mundane cases, we've seen services disappear without warning, leaving sites using them stuck trying to load scripts that no longer exist.
Real World Impact
The day-to-day end result of poor front-end performance has been well documented, and Google recently announced they will be using site speed as a ranking factor for mobile search in addition to desktop, putting added pressure on webmasters to ensure their site loads quickly.
So, what can you do? As with most things, there's no simple answer that's right for everyone. Just bear in mind every feature you add to your website comes at a cost. Don’t let that put you off — most third-party scripts now behave well, and have minimal impact on performance. But before adding that extra analytics script into Google Tag Manager, or asking your dev team to plug that fancy widget into the footer, ask yourself whether the benefits it brings are worth the performance cost to your users. If you normally use your site on the office wifi, try it on a mid-range Android device, on a mobile network (or try using Chrome’s developer tools to simulate different devices). Does it feel fast? Do things seem to move about on the page while it loads?