Making decision: hosting of javascript libraries on external CDN or locally

The benefits of hosting common JavaScript libraries externally at JavaScript CDN are well known - i list them just in short: external hosting of JavaScript libraries

• reduces own server's traffic
• makes parallel loading possible

The first question is: where to host? Directly on library vendor's site? Or somewhere else? There are mainly two factors, which let us make a decision, where we host our JavaScript libraries:

• Speed
• Popularity

The second question is more general: whether to host externally? Or locally?
Lets look on some details, which help to choose an optimal public hosting of common JavaScript libraries.

tl;dr;

• If you doubtlessly want to host JavaScript libraries externally, host them at Google Hosted Libraries - so you get highest chance, that your visitors have them already in chance and don't need to download them again.
• If you doubt, host better your JavaScript libraries locally - visitors, who have JavaScript libraries in cache are very few, and the average visitor gets the data on fastest way.

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