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Add-ons using the techniques described in this document are considered a legacy technology in Firefox. Don't use these techniques to develop new add-ons. Use WebExtensions instead. If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions.

From Firefox 53 onwards, no new legacy add-ons will be accepted on (AMO).

From Firefox 57 onwards, WebExtensions will be the only supported extension type, and Firefox will not load other types.

Even before Firefox 57, changes coming up in the Firefox platform will break many legacy extensions. These changes include multiprocess Firefox (e10s), sandboxing, and multiple content processes. Legacy extensions that are affected by these changes should migrate to WebExtensions if they can. See the "Compatibility Milestones" document for more.

A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.


Constructor for a console instance.


The plain-text console is a constructor for creating a console object to be used for traditional logging purposes. It's implemented using Console.jsm, and is prefixed with the addon's name, and log levels set based off of startup instruction. An instance of the console is injected globally into addon's contexts.




Creates a console instance. All of its methods are inherited from Console.jsm (resource://gre/modules/devtools/Console.jsm).


print : Function
An optional function to process the arguments passed in before printing to stdout.

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 Contributors to this page: wbamberg, jsantell
 Last updated by: wbamberg,