For a near-complete list of Modules in MLN, see List of Modules.

Modules are publicly visible mini-applications within users' Public Pages that usually perform special functions and interact with visiting users. Modules have various functions, such as sending out Items, Loops, and Stickers to random members on the owner's friend list, converting an Item into another Item, giving Items to visiting users, showing off Item collections, generating a specific item, and so on. Like most Items and Badges, all Modules have blueprints.

Modules can take up a number of slots on a user's Public Page or Page Builder. Each Public Page has 12 slots available in a three-by-four grid. This limits the number of Modules which can be placed on a Public Page. Some modules are three slots wide such as the Dinosaur Excavation Module, others have two such as the Factory Module, and others take up only one slot such as the Orange Mixing Truck Module.

There are some fundamental properties that characterize Modules:

All Modules take Votes (clicks) from visiting users. Most Modules give an advantage to the owner per a certain number of click(s). To click on a Module, a visitor must click on the Vote button ( Vote Button ). Occasionally, this button does not appear on the page; this usually means the owner has not "set up" the Module since the last click (see below) or the page visitor is out of clicks.

Most Modules grow a number of Items per day on a given basis. The most well-known is the LEGO Tree Module, which grows 10 Red LEGO Bricks per day. When Items are available for harvest, they can be collected by clicking the Harvest button ( Harvest Button ) on the Public Page. Modules have a limit on the number of Items the Module can grow between harvests; this is known as the harvest limit. When the number of Items stocked within the Module meets the harvest limit, the Items stop growing.

Some Modules need to be "set up" by the owner before clicking and other functions are enabled. This is done by clicking the Setup button ( Setup Button ) on the Public Page and giving up an Item so that it is "inside" the Module. If the Module has not yet performed its action, the owner may recover the Item at any time by pressing the Tear Down button ( Tear Down Button ) on the Public Page. Upon performing the Module's action, the Item used to set up the Module is usually lost, and the owner must set up the Module with another Item before continuing. The first Module like this is the Hive Module.

Players can find information on a particular Module by hovering over the Module in the Public View. It will display a brief description on how the Module behaves, although these descriptions are known to be occasionally incorrect (some purposely so, however) such as the Dino Ambush Module, Rank 1.

There are some Modules that players cannot obtain, e.g. the Networker Trade Module and Networker Text Module. Players informally refer to these as "Networker Modules."

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