Wi-fi is a set of standards for technology allowing computers and other devices to communicate using radio connections instead of cables. It was originally intended to allow the replacement of the cables which commonly connect computer networks on a single site with more convenient radio links. It has proved to be useful well beyond this limited role.

Wi-fi is also known as WLAN, because it is a wireless type of local area network (LAN).

One particularly important application is the use of wi-fi for mobile internet access. Its main competitor in this role are 3G mobile phone networks. In comparison to them:

  • Mobile networks provide extensive coverage, covering whole countries. Wi-fi provides coverage in "hot spots" and even city wide coverage is only now becoming common.
  • Wi-fi requires much cheaper infrastructure. It is so cheap that some cities are building free wi-fi networks and cafés and airports offer free hotspots. Even some private individuals provide free internet access through a single hotspot.
  • Wi-fi uses unregulated spectrum (radio frequencies) so the barriers to entry are much lower.
  • Mobile networks can provide uninterrupted connections to moving equipment.

Because of its low cost and the increasingly wide availability of equipment (such as laptop computers) that can use wi-fi, it is a serious threat to mobile phone networks' data revenues.