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What are intranets and extranets?

Man with two computer screens

You know a little about your company’s intranet, but what exactly is it - and what’s the difference between an ‘intranet’ and an ‘extranet’? Our short guide should clear up any confusion.

Jack Schofield | 9th September 2010

An intranet is a private network, operated by a large company or other organisation, which uses internet technologies, but is insulated from the global internet.

An extranet is an intranet that is accessible to some people from outside the company, or possibly shared by more than one organisation.

For decades, many organisations have used in-house networks to connect their computers and make applications available to their staff. These networks were often expensive and could be hard to use. When the internet became popular, its networking software became widely available and, usually, free. It therefore made sense for organisations to adopt the same software for internal use.

What intranets do

Intranets typically start by publishing web pages about company events, health and safety policies, and staff newsletters. Popular applications follow, such as forms to reclaim expenses or request holidays. All these help eliminate paperwork and speed up workflows.

As more features are added, an intranet can become essential to the operation of an organisation. It becomes a portal that provides access to all the things workers need.

The intranet is protected from the global internet by firewalls and by the need to log on with a secure password. Staff working outside the organisation may be able to access the intranet by using a VPN (virtual private network). This means all communications between the intranet and the user’s personal computer are encrypted.

What extranets do

Extranets take this process a step further, by providing access to people who work for different organisations. For example, a company could provide access to a supplier for online ordering, order tracking and inventory management. Instead of sending information to suppliers, it lets them fetch it on a self-service basis. Another example would be a hospital providing local GPs with access to a booking system so they can make appointments for their patients.

An extranet should be more efficient because everyone has access to the same data in the same format. Because all extranet communications can be encrypted over a VPN, it should also be more secure than sending data over the public internet.

Potential drawbacks

In practice, there can be drawbacks to intranets and extranets. IT staff are not website developers - they don’t have to work with dozens of browsers on millions of different PCs, just the company standard.

Also, in-house developers expect applications to last for many years, perhaps for decades, whereas websites can change every few months as web standards and fashions change. This means companies can get stuck with an obsolete browser, such as Microsoft’s Internet Explorer 6, because vital internal applications have not been tested against or adapted for more modern browsers.


Jack Schofield

Jack Schofield

Jack Schofield is a technology journalist and blogger who covered IT for the Guardian from 1983 to 2010. Before specialising in computing, he edited a number of photography magazines and books.