| File | Provides | Description |
| Core | Core, MooTools, Type, typeOf, instanceOf, Native | The heart of MooTools. |
| Array | Array | Contains Array Prototypes like each, contains, and erase. |
| Function | Function | Contains Function Prototypes like create, bind, pass, and delay. |
| Number | Number | Contains Number Prototypes like limit, round, times, and ceil. |
| String | String | Contains String Prototypes like camelCase, capitalize, test, and toInt. |
| Browser | Browser, Window, Document | The Browser Object. Contains Browser initialization, Window and Document, and the Browser Hash. |
| Class | Class | Contains the Class Function for easily creating, extending, and implementing reusable Classes. |
| Class.Extras | Class.Extras, Chain, Events, Options | Contains Utility Classes that can be implemented into your own Classes to ease the execution of many common tasks. |
| Class.Thenable | Class.Thenable | Contains a Utility Class that can be implemented into your own Classes to make them "thenable". |
| Object | Object, Hash | Object generic methods |
| Slick.Parser | Slick.Parser | Standalone CSS3 Selector parser |
| Slick.Finder | Slick.Finder | The new, superfast css selector engine. |
| Element | Element, Elements, $, $$, IFrame, Selectors | One of the most important items in MooTools. Contains the dollar function, the dollars function, and an handful of cross-browser, time-saver methods to let you easily work with HTML Elements. |
| Event | Event | Contains the Event Type, to make the event object cross-browser. |
| Element.Event | Element.Event | Contains Element methods for dealing with events. This file also includes mouseenter and mouseleave custom Element Events, if necessary. |
| Element.Delegation | Element.Delegation | Extends the Element native object to include the delegate method for more efficient event management. |
| Element.Style | Element.Style | Contains methods for interacting with the styles of Elements in a fashionable way. |
| Element.Dimensions | Element.Dimensions | Contains methods to work with size, scroll, or positioning of Elements and the window object. |
| Fx | Fx | Contains the basic animation logic to be extended by all other Fx Classes. |
| Fx.CSS | Fx.CSS | Contains the CSS animation logic. Used by Fx.Tween, Fx.Morph, Fx.Elements. |
| Fx.Morph | Fx.Morph | Formerly Fx.Styles, effect to transition any number of CSS properties for an element using an object of rules, or CSS based selector rules. |
| Fx.Transitions | Fx.Transitions | Contains a set of advanced transitions to be used with any of the Fx Classes. |
| Fx.Tween | Fx.Tween, Element.fade, Element.highlight | Formerly Fx.Style, effect to transition any CSS property for an element. |
| Request | Request | Powerful all purpose Request Class. Uses XMLHTTPRequest. |
| Request.HTML | Request.HTML | Extends the basic Request Class with additional methods for interacting with HTML responses. |
| JSON | JSON | JSON encoder and decoder. |
| Request.JSON | Request.JSON | Extends the basic Request Class with additional methods for sending and receiving JSON data. |
| Cookie | Cookie | Class for creating, reading, and deleting browser Cookies. |
| DOMReady | DOMReady, DomReady | Contains the custom event domready. |
