Load Time is the total time it takes for a web app or site to load.
The goal of a performance site is to have all of the site – or at least most of it – loaded within 2 seconds.
If your app takes more than 4 seconds to load, chances are you have lost more than 25% of your users.
Latency
Latency is where time is added to the total download time of a website waiting to download additional assets. The larger the files, the longer the latency. Latency is an issue mainly affected by the Head of Line Blocking issue, when a request is stuck waiting for another request to be completed.
Good Load Time
Load time is defined by the following 3 concepts:
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Perceived Performance
A metric for how fast user’s think your site is. This is more psychological than technical.
Developers can use techniques that load the essential code and data first, and then progressively load the rest in the background or on demand.
This gives the user the experience that the site is loaded when it actually hasn’t completed yet. -
First Meaningful Paint
A perceived performance metric where the user first sees content appear in the client post request.
This goes hand in hand with perceived performance. Instead of staring at a blank screen for three seconds, a user should have a first view pretty quick.
Above the Fold (AtF) Inline Styling
Essential assets (i.e. CSS, JS, and images) to the initial load of the site or app within the constraint of the first view.
In other words, the content required for the user’s first interaction that are visible without scrolling.
Above the fold for mobile sites refers to the initial content that appears before the user scrolls the app. -
First Available Interaction
A metric that closely associates with First Meaningful Paint where the user is able to begin interaction with the content of your site/app.
This is when a user can actually use the site/app. If the site/app visually loads but none of the actions work, then the it is essentially broken.