Apache and IIS are the most common web servers in use today, but they are far from alone. There is a huge amount of web server software out there, both free and commercial.

In this article we present four popular alternative web servers: Lighttpd, Nginx, LiteSpeed and Zeus. The first two are free and open source while the other two are commercial, closed-source alternatives. What they all have in common is that they focus on high performance.

We will also take a look at how many websites are actually using these web servers.

But first a brief presentation of each of one:

Lighttpd

• Brief info: Pronounced “Lighty”, Lighttpd is as the name implies a small, lightweight web server which has a low memory footprint and light CPU load. Lighttpd is a good alternative to serve static content but it has also gained recognition in the Ruby on Rails and PHP communities.
• Used by: Wikimedia (Wikipedia), Sourceforge, YouTube, The Pirate Bay, Meebo, Imageshack, Sendspace, Mininova.
• Cost: Free
• Open Source: Yes
• OS platforms: Linux, freeBSD, Solaris, MacOS X, Windows (under Cygwin)
• Homepage: www.lighttpd.net

Nginx

• Brief info: Pronounced “engine X”, Nginx is a lightweight web server and reverse proxy. Originally written by Igor Sysoev for Rambler.ru (Russia’s second most visited website). Nginx is known for stability and simple configuration in addition to its low resource consumption. It can also act as an IMAP/POP3 proxy.
• Used by: Yellow Pages, Hulu, Zimbra, the Friends for Sale Facebook app, Rambler, and it also seems that Wordpress.com just started using it instead of LiteSpeed.
• Cost: Free
• Open Source: Yes
• OS platforms: Linux, FreeBSD, Solaris, MacOS X
• Homepage: www.nginx.net

LiteSpeed

• Brief info: LiteSpeed is a commercial web server designed specifically for large websites. One of LiteSpeed’s advantages is that it can read Apache configurations directly which makes it easy to integrate with existing products to replace Apache. The server is lightweight and as the name implies very fast.
• Used by: Wordpress (until recently at least, but now Wordpress.com appears to be using nginx), Twitter, GigaOm, Bravenet.
• Cost: Free to $1,299 depending on the edition.
• Open Source: No
• OS platforms: Linux, FreeBSD, Solaris, MacOS X
• Homepage: www.litespeedtech.com

Zeus

• Brief info: Zeus web server is a high performance web server. It has received PC Magazine Editors’ Choice award and also the eWeek/PC Magazine Innovation in Infrastructure award. Zeus is a highly flexible enterprise product.
• Used by: Sony, Telefónica, Virgin media, phpBB.
• Cost: $1,700 up to two physical CPUs; $850 per additional CPU.
• Open Source: No
• OS platforms: Linux, FreeBSD, Solaris, HP-UX
• Homepage: www.zeus.com/products/zws

How many websites are using these web servers?

According to Netcraft, Lighttpd is currently the most common of these four web servers. On April 1, the numbers of websites for each were as follows:

Lighttpd: 1,495,308
Nginx: 1,018,503
LiteSpeed: 668,030
Zeus: 420,477

These positions were not always the same, though. As you can see by the following graph, which shows the numbers from January 2006 to April 2008, the situation has changed significantly over time.

The huge leap for Lighttpd in January-March of 2007 is most likely due to one or more web hosting or domain registration companies switching over to Lighttpd either for their regular pages, or for parked pages, or both. If anyone knows what happened there in more detail, please feel free to let us know in the comments.

Interestingly, the number of servers using the Zeus web server has remained quite constant over the last two years, and even decreased a little. That said, it is mainly an enterprise solution, so this is perhaps not so surprising.

The two web servers that have been growing the fastest lately are Nginx and LiteSpeed. Nginx recently passed the one-million-websites mark.

These numbers of course still pale next to Apache’s roughly 83 million websites, but there is no doubt that these alternative web servers are gaining in popularity. Who knows, one of them may be just right for you?