http with or without www

[alen]

I wanted to ask why someone might want to have their url without www in it?  Is this related to the company that hosts the domain or the website server or something like this?  Or is there another reason for wanting to leave off the www?

[Salmon Trout]

The www is not compulsory or necessary so an equally valid question is why anyone would want to have a web address with www included. Sometimes the decision is made to not use it. Some sites have www and non-www addresses.

[camerongray]

Most websites will work without www. without any extra configuration - I never use www.

Some websites don't work without it but that is usually down to bad server configuration.

[Computer Hope Admin]

May also want to see our URL definition page, which breaks down the full meaning of the URL, including the www. Also, a great shortcut key for those mentioning they don't type the www is CTRL + ENTER, pressing this after typing a domain will fill everything else out. For example, type computerhope in the address bar and then press CTRL + ENTER to fill out the http://, www. and the .com. 

[kpac]

www is taken as the default subdomain for most websites, configured on the server. It's usually good practice for webmasters to redirect the non-www to www version (or vice versa) to allow for canonical links.