Cloudflare is a free or cheap CDN. This review relates to the free version. There are plenty of other explanations of how this works, so I will not repeat them here, beyond saying that it is a network of servers around the world which should serve static content, such as images and css files, from a server local to the client. Cloudflare also increases security by challenging automated attempts to access the site from spam and hacking bots.
My experiences with Cloudflare.
There is a free version, and a ‘Pro’ version which provides prefetching of web pages it thinks the client may want, and enhanced security. There is a saying that if it sounds too good to be true, it probably is. However, during the dot com bubble there were many good free services. Whether or not Cloudflare will be able to continue this business model, who knows. For now it seems excellent. I have not been with Cloudflare long enough to comment on their Analytics.
Downsides
I have only had an account for a couple of days and comment on this. The additional layer of caching is extremely irritating when you are constantly editing the site, notwithstanding that Cloudflare has a development mode.
Cutting spam
My website is fairly new and the bots have not found it yet. I do not yet know whether I need anything over and above the spam protection already installed. Other reviewers report positively on this aspect of Cloudflare, which has to be worth having, provided there are no false positives, challenging genuine visitors. I have not been using Cloudflare long enough to know, and of course one rarely gets to hear of a genuine visitor turned away.
Cloudflare adds to, but does not replace, tuning the server and site for speed
I have done a lot of work to get this website working fast. There is no substitute for tuning the server and website by hand for your needs. Cloudflare is only serving static content, so the speed of generation of your page, by WordPress or Drupal or whatever CMS you are using, is still down to your own server. If you are going to tune that server to be fast, and if you are using Cloudflare, you need to think through the additional implications for how to set up the server, rather than just switch on Cloudflare and forget it. Having said that, if your approach is to make the most of the server or hosting account you have, without a lot of tinkering to improve performance, it is safe to just switch Cloudflare on, and you can reasonably expect an improvement in performance. That is especially true if you are on a low grade hosting account or an overworked server.
Cloudflare support
The emails back from staff are friendly and helpful. When I sent a request at the beginning of the weekend, I had to wait until Monday for a reply. I cannot complain about that with a free service! Even with their paid service, considering its low price, this would be acceptable IMO.
Speed tests on Cloudflare
Impressionistic speed tests, with and without Cloudflare, from same location and time of day, two days running: very hard to say whether Cloudflare improves speed, but on the whole page load times using Cloudflare have been a positive experience.
Timing page load with Firebug, with and without Cloudflare, from same location and time of day: hard to judge because the browser cache may contribute to load times, and various other factors, especially with multi-layer caching on the server.
After several page views I was getting these average times (averages of load times to view seven or eight different pages on the site):
page size first page lookup browser refresh
with
Cloudflare: 8.34m 1.63s (onload 2.73s) 2.35s (onload 4.4s)
without
Cloudflare: 6.1mb 1.32s (onload 2.48s) 1.65s (onload 4.02s)
The first page lookup might have been pulling some files from the browser cache, so I take the figures for refresh times as more reliable. On this basis, Cloudflare wins.
Webpagetest.com results, testing from Paris, and Dulles TX. I ran about 15 of these tests. Results are variable, of course.
The results without Cloudflare, for the dedicated server, running Varnish (but a poor hit rate for WordPress, a problem I am working on!), and with W3 Total Cache page cache enabled, gave speeds in the range of 2.3s-3.7s (excluding a few slow ‘outliers’). The slowest page loads I saw with Cloudflare were 2.3s. If they are claiming an average improvement of performance of 30%, I would not argue.
Takeaway conclusions from review of use of Cloudflare on Classics Blog
Cloudflare is worth using because it gives some speed advantage. It adds to rather than replaces the need to tune your website and server. It is not only for sites on slow servers, either (though keeping bots out and saving bandwidth is more important if you are underpowered). The claimed security advantage and the analytics are probably worth having but it is too soon for me judge. Cloudflare support is good considering the price. Downtime: who knows? So far, so good.