An online pass is a system of restricting access supplemental functionality in a product through a single-use serial number in order to hinder or discourage the second-hand sale of a product, and to allow the producer of a product to still return profits from second-hand copies of the product.
A similar tactic has also surfaced in the academic textbook industry, requiring use of a similar access code to access supplemental material and other online content (such as an online message board and integrated learning management system for submitting assignments). The system intends to prevent students from obtaining a second-hand or borrowed copy of a needed textbook, thus requiring them to purchase a new copy in order to use its functionality.
Video games 
The use of online passes in video games is intended to, alongside downloadable content, counter the popularity of chains such as Gamestop (which buy and sell second-hand copies of video games) by allowing a publisher to make up for profits lost through the second-hand sale of video games by receiving revenue through alternate means. Typically, these passes will restrict access to the game's online content, most notably multiplayer features. If a player does not have an unused online pass (such as when buying a used game), the player can either purchase access via their console or can access a limited (commonly 2 day) trial of the game's online content.
Supporters of online passes and publishers using them argue that requiring buyers of used games to pay extra for access to online content and services is a more fair system for paying the costs required to maintain online resources. Opponents contend that adoption of online pass systems may lead to removing more essential functionality from used games and possibly even preventing the resale of video games.
Publishers utilizing online passes 
- 505 Games
- Electronic Arts (2010-2013) 
- Sony Computer Entertainment
- Warner Bros. Interactive Entertainment
A similar system has been recently used by textbook publishers, by requiring the use of an online pass to offer supplemental content; including an online message board, an assignment system where homework may be assigned or handed in, or even an e-book version of the title. It is similarly intended to discourage the second-hand re-sale or sharing of these textbooks by only allowing their online functionality to be utilized by a single student; requiring others to buy their own copy of the book or obtain an access code individually.
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