HTML `link` for Prefetching DNS
Pre-resolving DNS can speed up page loading speed, and using HTML link tags for DNS pre-resolving is an effective method; DNS Prefetching analyzes domain names in advance through <link rel="dns-prefetch" href="//example.com"> to save subsequent request time; applicable scenarios include third-party fonts, advertising statistics scripts, resource hosting and CDN domain names; it is recommended to prioritize the main page dependency resources, reasonably control the number between 3 and 5, and use it with preconnect better.
Let me directly talk about the key points: parsing DNS in advance can speed up page loading. Using HTML link
tags to perform DNS pre-parsing is a simple and effective method.

What is DNS Prefetching?
Simply put, DNS resolution is the process of converting a URL (such as example.com) into a server IP address. Although this process is not long, it takes time every time. If you tell the browser in advance: "I may access this domain name later", it can parse in advance when it is free, saving loading time.
Using DNS Prefetching is to use the HTML <link>
tag to let the browser do this parsing action in advance.

How to use link
to do DNS Prefetch?
Just add this code to of the page:
<link rel="dns-prefetch" href="//example.com">
Pay attention to a few points:

-
rel="dns-prefetch"
means this is DNS pre-resolution -
href
value can be a domain name or a protocol, but it is usually enough to just write the domain name. - The protocol part can be omitted (using
//
), so that the browser will automatically select http or https based on the current page.
For example, if you use Google Fonts, you can write this:
<link rel="dns-prefetch" href="//fonts.googleapis.com">
Which situations are suitable for DNS Prefetch?
Not all external links are worth pre-parsing, just choose a few key ones:
- Third-party font services (such as Google Fonts)
- Domain name for ads or statistics scripts (such as Google Analytics)
- Image or video resource hosting domain name
- CDN Address
But note that if the current page does not access these domain names at all, there is no need to add them. Adding a bunch of them may waste browser resources.
Some practical suggestions
- Prioritize external resources that the main page depends on , such as fonts, scripts, and image CDNs
- If you use multiple subdomains, such as
img1.example.com
andimg2.example.com
, you can only pre-resolve the main domain nameexample.com
, and the browser will usually automatically recognize and apply it to the subdomain name - Don't abuse it, usually 3 to 5 are almost the same
- It can be used with
preconnect
, first DNS resolution and then establish a connection, which has better effect
Basically all this is not complicated but easy to ignore. The rational use of DNS Prefetch can make page loading smoother, especially when the mobile terminal or network is slower.
The above is the detailed content of HTML `link` for Prefetching DNS. For more information, please follow other related articles on the PHP Chinese website!

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