Speculative loading:-
The technique of carrying out navigational operations (such DNS querying, resource fetching, or document rendering) in advance of the related pages being visited—based on educated guesses as to which pages the user is most likely to visit next—is known as “speculative loading.
These predictions can come from browser heuristics (based, for instance, on popular sites in the user’s history) or from developers (for example, lists of the most popular destinations on their site). When implemented properly, these technologies can increase performance dramatically by speeding up the availability of pages—sometimes even instantaneously.
This page examines the various speculative loading methods that are available and when they should be applied to boost efficiency.
Speculative loading mechanisms:-
There are several mechanisms for speculative loading:
- Prefetching is the process of obtaining some or all of the resources needed to render a document—or a portion of a document—before those resources are needed. This allows for considerably faster rendering when the time comes.
- Going one step further, prerendering actually renders the content so that it is ready for display when needed. Depending on how it’s done, switching between the old and new pages may happen instantly.
- Preconnecting is the process of anticipatorily completing some or all of the connection handshake (DNS + TCP + TLS) in order to accelerate subsequent loads from a certain origin.
How is speculative loading achieved?
Speculative loading is achieved in two main ways. Initially, in order to automatically increase performance, some browsers will prerender websites depending on different heuristics. The specific method used for this relies on how the browser is implemented. When you type matching strings into the address bar in Chrome, for instance, the browser automatically prerenders pages if it believes there’s a good chance you’ll visit that page (for more information, see Viewing Chrome’s address bar predictions). Additionally, if the search engine instructs it to do so, it might prerender search results pages automatically when search words are entered into the address bar. It uses the same method as the Speculation Rules API to do this. Second, developers can specify exactly what kind of speculative loading they want the browser to do using a variety of platform characteristics. These are reviewed in the next section.
Speculative loading features
<link rel="preconnect">gives browsers a hint that the user is probably going to require resources from the origin of the specified resource; as a result, the browser can probably increase performance by opening a connection to that origin in advance. Partially or completely, supporting browsers will carry out the connection handshake in advance (DNS + TCP + TLS).
When should you use each feature?
The kind of speculative loading feature you choose will rely on the resources you wish to maximize, the degree of control you need, and your particular use case:
- Link Prefetching: Use this to prefetch resources (such as fonts, scripts, or essential assets for the following page) that you know you’ll need for future navigations.
- Resource Hints: These help maximize certain elements of loading resources, like DNS resolution.
(dns-prefetch), early connection establishment (preconnect), or background rendering (prerender). - HTTP/2 Server Push: If you are in charge of the server and know with certainty how many resources are required for a particular request, think about using server push. It can be especially helpful for pages that use a lot of resources or for pages that load slowly.
- Predictive Prefetching: Predictive prefetching is a fantastic option if you want to take advantage of browser-level intelligence without requiring direct developer participation. But be aware of the possibility of errors and the fact that you have no control over the prefetching behavior.
It’s also important to remember that these characteristics can be mixed and applied with other methods of performance optimization, like caching strategies that work, code splitting, and slow loading. Measuring and tracking the effects of speculative loading on your particular application is crucial for performance improvement, and you should modify your strategy accordingly.