.Mobi domain (also known as DotMobi) is a top-level domain approved by ICANN and managed by the mTLD global registry dedicated to delivering the Internet to mobile devices via the Mobile Web. It is financially backed by Google, Microsoft, Nokia, Samsung, Ericsson, Vodafone, T-Mobile, Telefónica Móviles, Telecom Italia Mobile, Orascom Telecom, GSM Association, Hutchison Whampoa, Syniverse Technologies, and VISA.

.Mobi domain names were made available for public registration on September 26 , 2006. Although introduced quite recently, .mobi has already made headlines with several 6-figure domain sales. .Mobi has also had its share of criticism due to allegedly breaking the principles of device independence. Some argue that providing content tailored to particular devices can and should be done by other means than a specific TLD, such as using hostnames within an existing domain, content negotiation through the HTTP protocol, cascading style sheets or other forms of adaptation.

Additionally, some have pointed out that ".mobi" is an unfortunate choice for mobile phone text entry interfaces, requiring nine or ten keystrokes in many common setups, compared to seven for "com", or what could have only been three if the more apt "wap" was used. However, there is a possibility that mobile phone manufacturers may in future default their mobile internet browsers to .mobi domain or that predictive-text input features will reduce this to one keystroke, either of which would effectively eliminate this issue.

Responding to criticism, .mobi engaged with the W3C Mobile Web Initiative (MWI) to help formulate the MWI Best Practices for mobile content. The practices outlined a number of ways to achieve good user experiences on mobile Web-enabled devices, and recognized several methods of implementing these practices.

mTLD has released a free testing tool called the MobiReady Report to analyze the mobile readiness of website. It does a free page analysis and gives a Mobi Ready score. This report tests the mobile-readiness of the site using DotMobi's recommended best practices.

Free authoring tools can be utilized to create mobi-compatible sites. mobi Site Galore is a free browser based tool that guarantees a fully standards compliant mobile website. Another is Mobilemo, which aside from creating mobi-compliant sites, provides interactive tools for a richer mobile experience.

The .mobi organization does not itself mandate any particular technology, but does require that .mobi sites produce user experiences consistent with their guidelines and specifically optimized for mobile phones.

Advantages of .mobi domain
Since 100% of .mobi sites must be optimized for viewing on a mobile phone, the main advantage of .mobi domain, from the users' perspective, is that they are guaranteed a site optimized for their smaller screens. Although a .com or any other extension can be optimized for mobile phones, in practice, only a fraction of them are, thus necessitating content adaptation solutions.

Disadvantages of .mobi domain
.Mobi recommends browser sniffing with Wurfl as a method for distinguishing between a mobile or desktop-based web browser . This risks creating two separate device-dependent World Wide Webs , one PC/desktop-based and the other mobile-based, and thus risks producing redundant content. In addition, use of the .mobi top-level domain is exclusive with any other top-level domain, and so, for example, a country code such as .UK or .JP cannot be used. A further assumption is that mobile devices all have similar screen sizes, user interfaces and connection speeds.