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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.

Starting from Firefox 53, no new legacy add-ons will be accepted on addons.mozilla.org (AMO) for desktop Firefox and Firefox for Android.

Starting from Firefox 57, only extensions developed using WebExtensions APIs will be supported on Desktop Firefox and Firefox for Android.

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 use WebExtensions APIs if they can. See the "Compatibility Milestones" document for more information.

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

Experimental

Enables you to read content from a URI.

Globals

Functions

readURI(uri, options)

Reads a URI and returns a promise.

Parameters

uri : string
The URL, as a string, to load.

options : object
Optional options:

Name Type  
sync boolean

If this option is set to true, the promise returned will be resolved synchronously. Defaults to false if not provided.

charset string

The character set to use when read the content of the uri given. Defaults to UTF-8 if not provided.

Returns

promise : The promise that will be resolved with the content of the URL given.

Document Tags and Contributors

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