HTML5Boilerplate, and others[citation needed], load jQuery this way, as we all know:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/vendor/jquery-1.10.2.min.js"><\/script>')</script>
Is this better for users? It's good practice to keep DNS lookups low, and unless we're also grabbing jQuery-UI or other frameworks from Google, then this is the only resource we get from their CDN. Would serving it from our own servers be faster?
Is this better for the server? Are we really saving that much by using Google's CDN for just this one relatively small file, rather than serving it ourselves?
Why just jQuery? Why just Google? HTML5Boilerplate includes normalize.css, and modernizr.js, both of which are popular files (arguably more popular and more of a staple than jQuery[disputed]) and are available at http://cdnjs.com/ and at a number of other CDNs. If we're loading jQuery, why not those 2? Is jQuery loaded from a CDN because it's deferred to load at the bottom of the page, and therefore it's OK to wait an extra .1s to get it from a CDN? I know Google CDN is a giant, but it's not unimaginable that other CDNs could handle a good amount of traffic.
Edit: Looking at Stack Overflow's code for this very page, they use their own CDN for 10+ resources, and then use Google for jQuery. There has to be a good reason for this, right?
Is this better for users?
Yes, especially popular libraries, because they might already be cached on the user's browser. Google servers are faster, and more reliable that your server; and so are most CDN's.
Is this better for the server?
Well, you serve less data.
Why just jQuery? Why just Google?
Not just jQuery, not just Google. The point is to use CDN when you can (and fallback to your server version) to benefit from speed and caching. Normalize is very small, but I think you can still benefit from using CDN. As for Modernizr, you want to be using a custom version, built for your needs, that's the recommended way to use the library.
Some of the said point of using a cdn is that users may have it in their cache and they will not have to download the file specifically for you website.
As for using Google CDN, They are huge and have amazing infrastructure; so why not?
Also I believe google is affiliated with html5boiler plate (At least one of the maintainers works for google)
When you pull jQuery from Google, there is a good chance it is already cached from a previous site, preventing an additional download.
We've discussed this question on the repo several times. This was the most recent. Lots of opinions, some testing, some super smart, super experienced people offering their 2 cents there. A fun, instructive discussion.
In general, anything you're wondering about with h5bp has been discussed in public somewhere.
To boil it down, the CDN is used because it's the best default configuration. If people download HTML5 Boilerplate and do nothing else to the code, having it linked to the Google CDN is the best default. It offers geographical optimization, fast servers, a cookieless domain and a chance of hitting the cache lottery.
It's also, by far, the most popular CDN, so if you're going to use a 3rd party service that's the one to use if you want a decent chance of getting a cached copy.
Again, there's a ton of detail in the issue if you have any other questions.
Related
My Shopify theme (New Standard) uses Google-hosted jQuery:
{{ '//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js' | script_tag }}
It doesn't work in China - researching on Stack Overflow reveals that Google-related content is frequently blocked by the great firewall, including stackoverflow.com itself.
Can I point the above line to another jQuery script file? Or is there a better way for my shopify site to be viewable in China?
Or could I simply download the .js file and upload it to my Shopify account and refer to it there?
I have very limited knowledge of JS so would appreciate if someone could point out any potential risks in doing this. Thanks.
You can refer it to anywhere. you can use Jquery CDN instead of google, if you can't host it. If you can host it by yourself, then that is the best option.
When it comes to commercial application, it is always safe to avoid dependencies like this. When we rely on other non paid CDN, it might be blocked, taken down or stopped who knows.
Always use local versions for commercial applications.
Other than Google CDN there are many more CDN available in market, but better to go with self hosted files as it will reduce dependency.
The safest way is to just upload the file to your server. You will need a bit more bandwidth and the initial loading time of the page may be a bit longer, but you can be sure that it works.
There are countless other CDNs for jQuery, for example //cdn.jsdelivr.net/jquery/2.1.1/jquery.min.js . It's unlikely that this one will be blocked, but you never know.
When page-load speed is the priority, is it better to use a minimal, lightweight javascript library (hosted on a CDN), or is it better to use something like jQuery, hosted on Google's CDN that the browser more than likely already has loaded?
Edit: What my question really boils down to is whether the cross-site caching effect of using jQuery hosted on Google's CDN outweighs the benefits of using an ultra-light library, also on a CDN.
jQuery is not heavy as compared to any other javascript library at present looking at the amount of features and browsers it supports.
You can consider this factor while selecting the plugins to be used on the page because they are written by various users and some may right it intelligently considering this factor or some may just right it for the sake.
Yes, if you use CDN like Google for jQuery it is most likely that the library must be cached by the browser and also Google has number of servers based on location so you don't have to worry about it.
Decreased Latency
A CDN distributes your static content across servers in various, diverse physical locations. When a user’s browser resolves the URL for these files, their download will automatically target the closest available server in the network.
In the case of Google’s AJAX Libraries CDN, what this means is that any users not physically near your server will be able to download jQuery faster than if you force them to download it from your arbitrarily located server.
There are a handful of CDN services comparable to Google’s, but it’s hard to beat the price of free! This benefit alone could decide the issue, but there’s even more.
Increased parallelism
To avoid needlessly overloading servers, browsers limit the number of connections that can be made simultaneously. Depending on which browser, this limit may be as low as two connections per hostname.
Using the Google AJAX Libraries CDN eliminates one request to your site, allowing more of your local content to downloaded in parallel. It doesn’t make a gigantic difference for users with a six concurrent connection browser, but for those still running a browser that only allows two, the difference is noticeable.
Better caching
Potentially the greatest benefit of using the Google AJAX Libraries CDN is that your users may not need to download jQuery at all.
No matter how well optimized your site is, if you’re hosting jQuery locally then your users must download it at least once. Each of your users probably already has dozens of identical copies of jQuery in their browser’s cache, but those copies of jQuery are ignored when they visit your site.
However, when a browser sees references to CDN-hosted copies of jQuery, it understands that all of those references do refer to the exact same file. With all of these CDN references point to exactly the same URLs, the browser can trust that those files truly are identical and won't waste time re-requesting the file if it's already cached. Thus, the browser is able to use a single copy that's cached on-disk, regardless of which site the CDN references appear on.
This creates a potent "cross-site caching" effect which all sites using the CDN benefit from. Since Google's CDN serves the file with headers that attempt to cache the file for up to one year, this effect truly has amazing potential. With many thousands of the most trafficked sites on the Internet already using the Google CDN to serve jQuery, it's quite possible that many of your users will never make a single HTTP request for jQuery when they visit sites using the CDN.
Even if someone visits hundreds of sites using the same Google hosted version of jQuery, they will only need download it once!
It's better to use the library that best suits the needs of your application and your development team. A super-lightweight library might save you a few hundred milliseconds of load time, but may end up costing you in development hours if your team has significantly more experience with jQuery/MooTools/Dojo etc.
If new feature implementation and bug fixing is hindered by using a second-rate tool solely to improve load times, your users are ultimately going to suffer.
Besides Google Libraries API what other services are there for hosted javascript libraries?
Please only list trusted sources, not some unknown third party.
Microsofts CDN
http://www.asp.net/ajaxlibrary/cdn.ashx
Before you go in search of hosted JavaScript libraries, you should consider the fact that any JavaScript that you include in your web page runs within the context of your domain and can access any data rendered on the web page or that the user can normally access on your domain. Using Google's hosted JavaScript is fine, but if its some third party you never have heard of, you might want to think twice.
Perhaps it would be better to search for high-quality JavaScript libraries and download your own copy that you maintain within your domain on your own servers (and can audit for security purposes)?
Out of curiosity... what specific functionality are you looking for?
There's also Yahoo YUI (http://developer.yahoo.com/yui/) though I believe they only host YUI itself. Make sure you pay attention to Michael Safyan's answer, too - who you're willing to trust with your users' code should be a carefully made decision. Beyond that, if you're looking for generic JS hosting you should make sure you really need it - a minified version of jQuery or MooTools is incredibly tiny, and shouldn't make any real difference either to your server's CPU usage or bandwidth expenditure.
It also doesn't meaningfully affect the maintainability of your HTML or JS, and it introduces another point of failure in your implementation.
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We're currently pulling jQuery and jQueryUI (and jQueryUI CSS) libraries from the google CDN. I like this because I can call google.load("jquery", "1");
and the latest jQuery 1.x.x will be used.
Now I am to pull the libraries locally because of security.
I'm happy to pull them locally but I'm wondering what are some of the other benefits and pitfalls to watch out for?
I always use the CDN (Content Delivery Network) from Google. But just in case it's offline:
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script>!window.jQuery && document.write('<script src="jquery-1.4.2.min.js"><\/script>')</script>
Grab Google CDN's jQuery and fallback to local if necessary
Edit:
If you don't need to support IE6 and your site has partial https usage you can remove the http as well:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
The main benefit of having them on a CDN is that the files can be downloaded in parallel to files downloaded from your own website. This reduces latency on every page. So, the flip side of this is a pitfall of hosting locally - increased latency. The main reason for that is that browsers are limited in the number of connections that they can make at the same time to the same web domain. In IE6 this was defaulted to 2 concurrent connections to the same domain - shared between all open windows of IE!! In IE8+ it improved, defaulting to 6, which is inline with FF/Chrome, but still, if you have a lot of images and you are not using sprites, you will experience heavy latency.
Using a CDN, I would always set the library version explicitly rather than getting the latest one. This reduces the risk of new versions breaking your code. Not very likely with jQuery, but possible.
The other main benefit of using a CDN is reduced traffic on your site. If you pay per GB or you are on a virtual server with limited resources, you might find that overall site performance increases and hosting costs come down when you farm off some of your content to a public CDN.
Make sure you also read the other answer to this question by #Xaver. This is a very good trick
Others have covered the benefits. Pitfalls:
If you only include content from your own server, that's one server that needs to be running—and not blocked by firewalls etc—to make your site work. Pull script from a third party and now that's two servers that need to be running and unblocked to make your site work.
Any site you pull <script> from can completely control the user's experience on your site. If Google were feeling evil they could put something in their copy of jQuery to log your keypresses, steal personal information from the page you're on to tie into their web tracking database, make you post “I love Google!” comments to every form, and so on.
Google probably aren't actually going to do that, but it's a factor that's out of your control, and certainly something to worry about with other script-hosting services. There have been incidents before where stats scripts have been compromised with malware loaders.
Before including any script from a third party—even on one single page of your site—you must 100% trust them with all user-accessible functionality visible on that hostname (including web-facing admin functions).
Google CDN:
caching, good for performance, more users likely to have it already, and it downloads in parallel
if ever, heaver forbid cdn goes down. you're screwed.
if a new version breaks your existing plugins or site, you'll know about it possibly too late
Locally:
development without being connected to the net is possible
can still get some performance benefits by gzipping, in addition to minifying
I prefer to use my local version, because I don't have control about what they will provide.
For example I don't want my users to get affected by google-analytics or anything similar, because this is a legal problem in my country.
Benefits: (Specifically for Google's CDN)
Downloads in parallel with your files. Other answers address this further
Google's Servers are likely to be able to physically deliver the content faster
Common libraries and frameworks might already be on the user's machine, as the HTTP cache for a CDN is universal across all sites
Your bandwidth wouldn't have to go towards serving large library files
Virtually every way you look at it, using Google's CDN is a good thing.
Performance will be improved (albeit fairly marginally, unless your site is really busy), and the amount of data your servers have to transmit will go down (although jQuery isn't exactly a massive thing to download), etc.
The only reason you wouldn't want to use it is if you don't trust Google. By using it, you are effectively giving Google an additional window of information into your site's traffic profile, including knowledge of URLs that you may otherwise not want to make public (eg secure areas of your site).
If you are paranoid about security then this may be enough to persuade you not to use them (after all, hosting it yourself isn't exactly going to slow your site down to a crawl), but in general most people would take the pragmatic view that Google knows enough about their site already that adding this won't make much difference.
Probably I'm in minority nowadays, but I'd say that you don't want to use CDN unless you really need to. Key factors to start using it are:
Cross geo users. If you host your website in the US but have visible amount of European users - CDN will improve the loading time.
Big amount of users and\or big content, so one main server is not enough any more. One can think of any porn-video website (or Netflix, if you want). Video stream is a heavy load, with CDN would be much much less load on the main server.
But... the point is that these points are not really applicable to 90% of websites in the world. I bet you're not Facebook with millions of online users around the globe, you're not Pornhub with hundreds of GB transferred every second.
If your website is targeted to users in your city/country and capacity of one server is enough for amount of users you have - why would you ever want a CDN? It's quicker for your users in your city and simpler for you to fetch everything from your main server locally.
It was more about CDNs in general, now let me be closer to the actual question about jQuery or any other library.
If you want your website to stay accessible and working without maintenance for more than a year, let's say - put it locally. Libraries nowadays are being updated in a crazy tempo which you probably don't want to follow. And old versions are being deleted eventually. Moreover, the whole library can die (probably not applicable to jQuery though).
From my recent experience - I updated TinyMCE on the website I maintain from 3.x.x (dated 2012) to 5.x.x (dated Spring 2019). This website was working for 7(seven!) years without any maintenance in this part of the logic. There was no "minifying" concept back then and CDNs were not as common as now. But even if they would be common - you never know what will happen in 3-5-10 years from now. Usually you want your website to stay alive even without you maintaining it, don't you? However if you pull jQuery from CDN today, then this link may (and, probably, will) break in 5 years.
Solution with CDN AND fallback to local version as #Xaver suggested can be a good compromise. But... maybe just get rid of CDN link? ;)
To me it really depends on how much control you desire to have. If you are like me and need to develop on local host when working and traveling. Having the jquery files local is better than having it hosted on google or else where.
I'm looking for the pros/cons of pulling jQuery & other JS libraries from Google API's cloud as opposed to downloading files and deploying directly.
What say you?
My decision
The likelihood of the lib already cached on the users system is the overriding factor for me, so I'm going with a permalink to googleapis.com (e.g. ajax.googleapis.com/ajax/libs/…). I agree with others here that loss of access to the Google server cloud is a minimal concern.
Con
Users in countries embargoed by the U.S. (e.g. Iran) won't get a response from Google
Pros: It may already be cached on the user's system. Google has big pipes. You don't pay for the bandwidth.
Cons: You now have two different ways for your site to become unavailable: A service interruption on your server or one on Google's server.
I've been looking at the real-world performance of the Google loader for jQuery, particularly, and here's what I've found:
Google's servers are quick and plenty reliable.
They are serving from a CDN, which means if you have a lot of overseas users they'll get much better load times.
They are not serving gzipped files. So they're serving a lot more bytes than they need to.
If you know what you're doing in Apache, Lighttpd, or whatever you're serving files with, you could set your cache headers just like Google's and significantly reduce the amount of data your end user has to download by serving it from your own server. You could also combine your scripts at that point and reduce your overall HTTP requests.
Bottom line: Google's performance is good but not great. If you have many many overseas users then Google is probably better, if your users are mostly US-based and maximum performance is your concern, learn about caching, Etags, gzipping, etc. and serve it yourself.
Pros:
Google's connectivity is probably way better than yours
It's a free CDN (content distribution network)
Your webapp might load faster, since you're using a CDN
Cons:
If/when you need to optimize by repackaging a subset of that third-party JS library, you're on your own, and your webapp might then load slower
In addition to points made by others I'll point out two additional cons:
An additional external HTTP request, so assuming you have a Javascript file of your own (almost certain) that's two minimum instead of one minimum; and
IMHO because jQuery load is async your entire page can load before the library has loaded so the effects that you do on document ready are sometimes visibly noticeable to the user when they are applied. I think this is not a great user experience.
The pros are quite obvious and are in the other answers :
you save bandwidth
google is probably more reliable than your server
probably cached in most browsers (anyone stats on this ?)
But the cons can be very tricky :
If you are using https, you will get an error on most browsers as your certificate isn't valid for google's domain, only yours. This is a major issue for https.
I think what would be cool to do is run A/B tests and see what the latency is to load minified version of jquery from Google's servers vs your server. Hopefully that'll put things into perspective. Chances are the Google server might be faster, but in terms of accepting responsibility of down time, nothing beats hosting it yourself.
Pro:
Google's Ajaxlibs offer a very fine-grained "version control" for the included libraries. You can enforce a certain version (e.g. JQuery 1.3.2) or automatically request the latest version from a certain branch (e.g. JQuery 1.3 series -> would currently deliver 1.3.2, but maybe soon 1.3.3).
The later has definitely has benefits: you'll profit from smaller bugfixes/performance improvements without breaking your scripts/plugins.
Maintaining such a multi-library repository on your own can become quite ressource intensive.
Con:
When afraid of DNS poisoning, or when afraid that some public wireless network might not be trusted, then the non-SSL versions might actually not be served by Google at all, opening up drive-by installation of malware. (But: caching is set to be a full year, so even though many browsers will issue a If-Modified-Since request for cached content when hitting refresh, this might still be a theoretical issue as most users will already have cached the resources while using another network.)
When taking extreme care for your visitors' privacy, you might not want Google to record visits to your site by using their CDN. (Quite theoretical as well, as the same note on caching applies.)