Checking someones bandwidth and loading content based on it

Question

I have seen a number of questions that don\'t answer this, is it possible to check someones bandwidth using java script and load specific content based on it?

The BBC se

Answer 1

While this isn't an answer, it may be important to note that measuring bandwidth isn't always reliable.

http://www.smashingmagazine.com/2013/01/09/bandwidth-media-queries-we-dont-need-em/

To paraphrase the above:

...the number of bits downloaded divided by the time it took to download them...is true when you download a large file over a single warmed-up TCP connection. That is rarely the case. Typical page load scenario:

1. Initial HTML page is downloaded using slow-start mechanism, so measurement will significantly underestimate the available bandwidth
2. CSS and JavaScript external resources are loaded -- a collection of new TCP connections, all in their slow-start phase, and they are not all necessarily to the same destination server
3. Images are loaded -- multiple connections, each one downloading a resource. The problem is that these connections are not always in the same phase of their life cycle. Some might be in the slow-start phase; some may have suffered a packet loss and, thus, reduced their window and the bandwidth they are trying to fill; and some might be warmed-up TCP connections, ready to fill the bandwidth. These TCP connections are not necessarily all to the same destination server, and the bandwidth towards the various destination servers might be different between one another.

So, estimating bandwidth is possible, but it is far from simple, and it is possible only for certain phases of the page-loading process. And because having several TCP connections to various destination servers is common (for example, a CDN could host the image resources of a Web page), we cannot really tell what is the bandwidth we want to measure.

Since this is an older question, the alternative suggestion at the end of the article is to consider the more recent srcset attribute for responsive imagery, which lets the browser decide which asset to load based on whatever it knows (which should be more than us). It sounds like it's weighted more towards just determining resolution, but maybe it'll get smarter as support goes up.