A concurrent user is a person who is accessing a system resource at the same time as one or more other users. Many computer programs support concurrent users. In the case of software, a software license may specifically limit the number of concurrent users a program will support; for example, teleconferencing software might support up to 20 concurrent users at any given time. Software companies use this as a way of providing multiuser functionality while still controlling how many people use their programs.
Concurrent users can view items like files simultaneously across a network, and they can also access software programs in similar ways. This allows offices to do things like buying one copy of a software program with attached concurrent user licenses so that everyone in the office can use the software. This is much cheaper than equipping each computer with a separately licensed version of the software and paying for each computer every time updates are released.
When people purchase software with concurrent user options, they are provided with information about how many concurrent users the software will support. Some companies require each user to be registered, while others allow a set number of unidentified users. If users are registered, the software may allow people to deregister people or devices and reregister different people and devices. This allows for flexibility in using the software without violating the terms of the software license.
With registered users, it can also be possible to set permissions. This allows a concurrent user different levels of control and access. In a teleconferencing program, for example, one user might have permissions to invite participants and terminate the teleconference, while others are invited as guests only and are not capable of controlling the conference itself. Varying levels of access can be important in a system where there are concerns about security or worries that a user could accidentally change a critical setting.
The Internet is heavily reliant on supporting concurrent users. Websites can support large numbers of users accessing the site and its resources at the same time for everything from browser-based games to chat clients. Without concurrent user functionality, people would have to wait for their time for online resources. People may note that websites tend to have a ceiling based on server capacity. Eventually, too many users will be logged on or visiting as guests and a site will begin to slow down.