Mobile Warning for Large Websites

This past weekend, I was poking around in the HTTP Archive, and I found a site with a 314 MB video that autoplays.  Now, there is a bug in Chromium where videos larger than 100 MB skip the cache – and I left the page open for a long time – so devTools told me the page had used 4.6 GB (!!!) of data. I tweeted the image because I thought it was funny, and it prompted a short discussion.  As often is the case, I learned about something new – a Chrome flag that will warn you when the page is using a lot of data:

Paul Irish replied to my Tweet with the Chrome Flag #enable-heavy-page-capping, which will alert you if the page is >5MB (or over 1 MB – depending on the setting).  I enabled it, and I started seeing this alert on my phone.   I began to wonder about alert fatigue – how often will this appear on mobile websites today?

Back to the HTTP Archive!  11% of mobile sites are >5MB, and 61% are over 1MB…  That seems like a lot of pages that would potentially throw the warning message.

How can we break this down further? How about by Top Level Domain (TLD)?  I limited the data to TLDs with over 400 entries in the HTTP Archive/

TLDs with highest % of sites over 5MB

The TLDs most likely to be over 5 MB are:

.to sites are probably vanity urls for other sites. The numbers quickly drop into the low 20% range.

TLDs most likely to be under 1 MB:

Again, Perhaps not a surprise, but .mobi – sites designed for mobile experiences – top this list.  Interestingly, .biz, .net, .info .io (popular with may startups)  and .coop all also appear high on this list as well.

What About PWAs

One point in the Twitter conversation asked if perhaps PWAs were caching too much information, and downloading a huge amount of data on initial load.

HTTP Archive has Lighthouse scores for each site, and this includes a PWA score – 0.75-1.0 is a passing score.  Of the 1.2M sites in the HTTPArchive, only 1636 sites score in this range.

Of the 1636 sites that pass the PWA Lighthouse test, 527 (32%) are over 1 MB, and 24 (1.5%) are over 5 MB – so while potentially an issue – PWAs are not the major cause of sites that use > 5Mb of data on the mobile web today.