Where do you include the jQuery library from? Google JSAPI? CDN?

Without a doubt I choose to have JQuery served by Google API servers. I didn’t go with the jsapi method since I don’t leverage any other Google API’s, however if that ever changed then I would consider it…

First: The Google api servers are distributed across the world instead of my single server location: Closer servers usually means faster response times for the visitor.

Second: Many people choose to have JQuery hosted on Google, so when a visitor comes to my site they may already have the JQuery script in their local cache. Pre-cached content usually means faster load times for the visitor.

Third: My web hosting company charges me for the bandwidth used. No sense consuming 18k per user session if the visitor can get the same file elsewhere.

I understand that I place a portion of trust on Google to serve the correct script file, and to be online and available. Up to this point I haven’t been disappointed with using Google and will continue this configuration until it makes sense not to.

One thing worth pointing out… If you have a mixture of secure and insecure pages on your site you might want to dynamically change the Google source to avoid the usual warning you see when loading insecure content in a secure page:

Here’s what I came up with:

<script type="text/javascript">
    document.write([
        "\<script src="",
        ("https:" == document.location.protocol) ? "https://" : "http://",
        "ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js" type="text/javascript">\<\/script>" 
    ].join(''));
</script>

UPDATE 9/8/2010 –
Some suggestions have been made to reduce the complexity of the code by removing the HTTP and HTTPS and simply use the following syntax:

<script type="text/javascript">
    document.write("\<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js" type="text/javascript">\<\/script>");
</script>

In addition you could also change the url to reflect the jQuery major number if you wanted to make sure that the latest Major version of the jQuery libraries were loaded:

<script type="text/javascript">
    document.write("\<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js" type="text/javascript">\<\/script>");
</script>

Finally, if you don’t want to use Google and would prefer jQuery you could use the following source path (keep in mind that jQuery doesn’t support SSL connections):

<script type="text/javascript">
    document.write("\<script src="http://code.jquery.com/jquery-latest.min.js" type="text/javascript">\<\/script>");
</script>