Why do browsers sometimes load pages twice?

[Safe-Keeper]

You know that thing when you open a new web page, and it'll load completely, only for the screen to go white and the loading to seemingly start anew from scratch, and only when it's done can you start navigating the web site? Ie. the website seems to need to load twice before?

I've had this happen a lot recently, and it happens both on my phone and laptop, so I assume it's the way the web site itself is programmed and not a problem with my particular device. So why does this happen?

 

[theprestige]

Could you give an example of a site that behaves this way for you?

My guess is, the site has a basic set of content that it starts loading by default, plus a number rules for variations of content and formatting to be loaded if certain conditions are met (certain cookies are present/not present; ad blocker on/off; the browser is in/out of a certain region; etc.).

So the server starts loading the default content and formatting, then discovers some other condition has been met, and starts reloading according to those conditions.

I suppose another possibility is some form of network weirdness, that allows a partial load and then reconnects, triggering a reload.

Or a partial load of a cached version of the content to be quicker, followed by a reload as the server realizes the cache is out of date.

The overall theme of these explanations is that there's an ideal setup where the server figures out all the conditional rules, cache freshness, etc. before it needs to reply to the browser. And what's causing the reload is some sort of lag in the server, between when it has to start loading the content and when it actually figures out what content to load.

 

[Darat]

As theprestige suggests I suspect it will be because it is using its cache of the page and then is informed it's out of date. With a good enough connection speed and a fast enough server you'd probably not notice it. However the way some sites, especially it seems "news" sites load their pages with video snips, interactive ads and so on any reload of the page is going to be noticeable. I've noticed some sites seem to need a complete reload even if you'd only opened it a few moments ago, probably to update the ads.

One of the worse offenders I've seen is the CNN site.

 

[theprestige]

I think a lot of news media companies see digital as superior to print because it gives them a lot more control over what content they can force on you.

A newspaper or magazine, you can just flip to the actual stories, and there's no autoplaying video following you from page to page.

 

[Dude111]

I have noticed that sometimes also on IE6 (MyIE2) so it doesnt matter the browser,we all have it happen...... (Must be ads or something causing the page to re-load??)