Microsoft CDN for jQuery or Google CDN? [closed]

Question

Does it actually matter which CDN you use to link to your jquery file or any javascript file for that matter. Is one potentially faster than the other? What other factors could play a role in which cdn you decide to use? I know that Microsoft, Yahoo, and Google all have CDN's now.

Answer 1

You should absolutely use the Google CDN for jQuery (and this is coming from a Microsoft-centric developer).

It's simple statistics. Those who would consider using the MS CDN for jQuery will always be a minority. There are too many non-MS developers using jQuery who will use Google's and wouldn't consider using Microsoft's. Since one of the big wins with a public CDN is improved caching, splitting usage among multiple CDNs decreases the potential for that benefit.

Answer 2

Update based on comments:

Short version: It doesn't matter much, but it may depend on what they host. They all host different things: Google doesn't host jQuery.Validate, Microsoft did not host jQuery-UI, since 2016 they do!!, Microsoft offers their scripts that would otherwise be served via ScriptResource.axd and an easier integration (e.g. ScriptManager with ASP.Net 4.0).

Important Note: If you're building an intranet application, stay away from the CDN approach. It doesn't matter who's hosting it, unless you're on a very overloaded server internally, no CDN will give you more performance than local 100mb/1GB ethernet will. If you use a CDN for a strictly internal application you're hurting performance. Set your cache expiration headers correctly and ignore CDNs exist in the intranet-only scenario.

The chances of either being blocked seems to be about equal, almost zero. I have worked on contracts where this isn't true, but it seems to be an exception. Also, since the original posting of this answer, the context surrounding it has changed greatly, the Microsoft CDN has made a lot of progress.

The project I'm currently on uses both CDNs which works best for our solution. Several factors play into this. Users with an older browser are still probably making 2 simultaneous requests per domain as recommended by the HTTP specification. This isn't an issue for anyone running anything decently new that supports pipelining (every current browser), but based on another factor we're knocking out this limitation as well, at least as far as the javascript.

Google's CDN we're using for:

• jquery.min.js
• jquery-ui.min.js.

Microsoft's CDN we're using for:

• MicrosoftAjax.js
• MicrosoftAjaxWebForms.js (until 4.0 we're not completely removing all UpdatePanels)
• jQuery.Validate.min.js

Our server:

• Combined.js?v=2.2.0.6190 (Major.Minor.Iteration.Changeset)

Since part of our build process is combining and minifying all custom javascript, we do this via a custom script manager that includes the release or debug (non-minified) versions of these scripts depending on the build. Since Google doesn't host the jQuery validation package, this can be a down-side. MVC is including/using this in their 2.0 release, so you could rely completely on Microsoft's CDN for all your needs, and all of it automatic via the ScriptManager.

The only other argument to be made would be DNS times, there is a cost to this in terms of page load speed. On Average: Simply because it's used more (it's been around longer) ajax.googleapis.com is likely to be returned by DNS sooner than ajax.microsoft.com, simply because the local DNS server was more likely to get a request for it (this is a first user in the area penalty). This is a very minor thing and should only be considered if performance is extremely important, down to the millisecond.
(Yes: I realize this point is contrary to my using both CDNs, but in our case the DNS time is far overshadowed by the wait time on the javascript/blocking that occurs)

Last, if you haven't looked at it, one of the best tools out there is Firebug, and some plug-ins for it: Page Speed and YSlow. If you use a CDN but your pages are requesting images every time because of no cache-headers, you're missing the low-hanging fruit. Firebug's Net panel can quickly give you a quick breakdown of your page load-time, and Page Speed/YSlow can offer some good suggestions to help.

Answer 3

As stated by Pingdom:

When someone visits your site, if they have already visited another site that uses the same jQuery file on the same CDN, the file will have been cached and doesn’t need to be downloaded at all. It can’t get any faster than that.

This means that the most widely used CDN will have the odds on its side, which can pay off for your site.

A few observations on performance: Google’s CDN is consistently the slowest of the three both in North America and Europe. In Europe, Microsoft’s CDN is the fastest.

Answer 4

Also consider when using Google CDN that some times people make typos such as ajax.googelapis.com. This could potentially create a really nasty xss (cross site scripting) attack. I have actually tested this out by registering a googlapis.com typo and very quickly found myself serving requests for javascript, maps, css etc.

I emailed Google and asked them to register similar CDN typo URL's but have not heard back. This could be a real reason not to rely on CDN's because there are potentially dangerous attackers awaiting the typo requests and can easily serve back jquery etc with an xss payload.

Thank you

Answer 5

Depending which industry the application targets, you may not want to use a CDN managed by other organisations. It often raises issues regarding to compliance, privacy and confidentiality.

For example, when you include Google Analytics in a secure application, the browser still sends the current URL as the "referer" header. Any identifiers, say a session id or secret token may appear in their logs. For example, if a client IP of 192.0.2.5references https://healthsystem.example/condition/impotence, then well, you can infer information which is considered to be rather private.

Other cases include information of consequence, such as an account number, social security number or session information in the URL. That sort of data should never be in the URL as it can be used outside of the application.

While you may trust Google, Microsoft or Yahoo, your users may not.

For industries like Finance, Legal and Health Care, you may want to establish your own CDN with the help of a vendor (e.g. Akamai) with which you can sign a BAA.

Answer 6

It's about statistics: jquery.com loads jQuery from Google. And so does Twitter, Stackoverflow and many many others. So, there are pretty high possibilities that your website user already have it cached = no download at all.

Forget validator, bandwith and speed because this is the major benefit. Otherwise, any other CDN option will perform essentially at the same level.