Should I use a hosted version of JQuery? Which one?

Question

Should I use a local copy of jquery, or should I link to a copy provided by Google or Microsoft? I'm primarily concerned about speed. I've heard that just pulling content from other domains can have performance advantages related to how browsers limit connections. In particular, has anyone benchmarked the speed and latency of Google vs. Microsoft vs. local?

Also, do I have to agree to any conditions or licenses to link from a third-party?

Answer 1

One advantage would be that a user may already have it cached since another site also linked to a 3rd party.

I've been using google for this and haven't experienced any problems with it so far. You can easily load jQuery using:

<script type="text/javascript" src="http://www.google.com/jsapi"></script>
<script type="text/javascript">
    google.load("jquery", "1.4");
</script>

Answer 2

Anytime you use an asset hosted by a third party you increase the number of possible points of failure in your application. You also risk potential bugs resulting from changes made to the asset (say, fixing a bug or updating to a new version) by the hosting party.

Page performance can potentially suffer due to latency differences between your site and the host. Network outages between the client and the host can cause your page to fail, as can internet filtering on the part of their ISP. For instance, using code hosted by Google will cause problems for anyone viewing your site from China.

It's better for security, performance, stability and version integrity to keep all of your assets in one place. Unless you're running a ridiculously high-traffic site, you shouldn't worry about distributing your content.

It's also worth noting that while jQuery isn't exactly a featherweight include, it's not obnoxiously large and, like any JavaScript includes, should be (but is not guaranteed to be) cached by the browser.

Answer 3

Most recommendations I have seen have been to use the hosted version of Google or Microsoft etc.

Dave Ward has a nice article explaining the reasons.

3-reasons-why-you-should-let-google-host-jquery-for-you

1. Decreased Latency
2. Increased parallelism
3. Better caching

See his post for stats.

Dave does point out that you should only do this for Public Facing websites.

Answer 4

I have been using Google's AJAX library hosting in production for several clients. Works like a charm, and is definitely the best way to go.

http://code.google.com/apis/ajaxlibs/