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 addons.mozilla.org (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.


Generate or parse UUIDs.


It exports a single function, uuid().

For more details about UUID representations and what they are used for by the platform see the MDN documentation for JSID.

Generate UUID

To generate a new UUID, call uuid() with no arguments:

let uuid = require('sdk/util/uuid').uuid();

Parsing UUID

To convert a string representation of a UUID to an nsID, pass the string representation to uuid():

let { uuid } = require('sdk/util/uuid');
let firefoxUUID = uuid('{ec8030f7-c20a-464f-9b0e-13a3a9e97384}');




Generate a new UUID, or convert a string representation of a UUID to an nsID.


stringId : string
String representation of a UUID, such as:


Optional. If this argument is supplied, it will be converted to an nsID and returned. Otherwise a new nsID will be generated and returned.



nsID : A UUID, represented as an nsID object.

Document Tags and Contributors

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