Dietrich recently posted about the memory usage of social plugins, and I found the results rather surprising because, at least in the case of Facebook, I didn’t think it ever loaded enough code to consume 20+MB of memory.
When I first learned about social plugins, I thought that they were a really cool idea and thought that they had a lot of potential. If they use a ton of memory though, I feel like it’s a bit of a deal breaker to using them. So, being the curious engineer that I am, I decided to test this out myself. I conducted these tests in a new Firefox profile and I was not signed into Facebook (to try and replicate the experience Dietrich had).
One Like Button
For my first test, I had a very simple page for the default like social plugin pointing to my site.
One like button doesn’t seem to add much, which is good!
Two Like Buttons
The next test I tried was duplicating the like button so it showed up twice. This code is a bit naive since I duplicate a <div> element with the same id and don’t need to include the JavaScript twice. However, it shows what someone who would just copy and paste will end up with, which I think is valuable.
As you can see, memory usage nearly doubled. This is a bit surprising since the exact same JavaScript is included. I would expect there to not be any additional shapes, but that nearly doubles. scripts and mjit-code also all double, and I would expect that at least the latter to not.
A more interesting version of this test would be to not include the JavaScript twice, and just add one additional <fb:like> button that doesn’t like the same url.
Interestingly, memory usage did not change significantly from the duplicate resource case! So, what exactly is going on here? This page ends up loading four additional resources:
| File | HTTP Status | Size | Mime Type |
| all.js | 304 | 143KB | application/x-javascript |
| login_status.php | 200 | 58b | text/html |
| like.php | 200 | 33KB | text/html |
like.php | 200 | 33KB | text/html |
That is 209KB of HTML and JavaScript that is being sent for two like buttons. Something tells me that part of the problem here is that Facebook is sending more than it needs to for this (I did not look into exactly what was being sent). The good news is that 143KB comes from the browser’s cache.
Send Button
The last test I did was the send button pointing to my website.
Given that the like button test includes a send button as well, I’m not surprised to see that this used even less memory.
Summary
I think there are are two problems here:
- Firefox should create less shapes and do a better job of not duplicating the same JavaScript code in a given compartment.
- Facebook needs to send less data down for their social plugins. I have a hard time believing that that much JavaScript is needed in order to display a like button, a share button, and a faces of your friends who have liked a page.
It’d be interesting to see how these numbers change when you are logged in, but I don’t have time to do that analysis. I’ve provided all the code and steps I used to get these results, so it shouldn’t be too hard for someone else to come along and do that if they are interested. Another interesting test would be to see how the Twitter and Google+ integrations break down too (but I leave that as an exercise for the reader).
