On Demand is a type of computer service where the software is presented to the user as soon as a subscription to the service is successfully processed. In a typical "on-demand" computing model, the software is not actually installed at the user device.  In the Software as a Service model  (SaaS model) it is accessed via the Internet from a centralized  location.

On demand contrasts with the traditional means of software delivery involving the physical distribution of software using a Disc or CD.   SaaS-Attack believes that the on demand services are becoming increasingly popular.

Advantages of the On demand service is that service can be instantaneous and can often run only as long as needed and then can be discontinued.  Subscription fees for a short period of use can often be less that the cost of purchasing software licences up-front.

Another advantage of On demand service is that the user can de-risk the acquisition of software by trialing an application to help ensure fitness for purpose.  In the physical software delivery model the Independent software vendor usually transfers the entire business risk to the customer.

By using an On demand service, the customer is able to avoid purchasing additional hardware and software infrastructure in order to run the application.  The customer is also able to avoid having to pay for the associated hardware and software maintenance fees.  The customer also transfers the burden of operations to the SaaS vendor.

Because of the many advantages, the On demand service is becoming increasingly popular with customers, who can concentrate upon using the software as opposed to provisioning it to run in house.  Also the customer can often avoid the delays and overhead associated with involving the IT department.