Add-on

Add-ons or expansions (also called expansion packs) are content created for games that are released separately from the main game release. Downloadable content (DLC) is a specific form of add-on distributed through the internet.

Fallout 3
The first game in the Fallout series to feature downloadable content was Fallout 3, with a total of five add-on packs released.
 * Operation: Anchorage (January 2009 for PC/Xbox, October for PS3)
 * The Pitt (March 2009 for PC/Xbox, October for PS3)
 * Broken Steel (May 2009 for PC/Xbox, September for PS3)
 * Point Lookout (June 2009 for PC/Xbox, October for PS3)
 * Mothership Zeta (August 2009 for PC/Xbox, October for PS3)

Fallout: New Vegas
Fallout: New Vegas has a total of four pre-order bonuses and six add-on packs. The pre-order bonuses were later condensed into the Courier's Stash add-on.
 * Dead Money (December 2010 for Xbox, February 2011 for PC/PS3)
 * Honest Hearts (May 2011 for PC/Xbox, June for PS3)
 * Old World Blues (July 2011)
 * Lonesome Road (September 2011)
 * Gun Runners' Arsenal (September 2011)
 * Courier's Stash (September 2011)

Fallout 4
Fallout 4 also features add-ons, with a total of seven add-on packs, of which two only include new settlement objects, and one is a graphical upgrade.

Fallout 76
Fallout 76 does not use add-ons and instead all updates are included with the game.