Arabeasy has a real advantage over other methods for western keyboards, using one letter per symbol and avoiding numbers or impractical symbols which are less accessible on smartphones.
follow these steps:
Currently only available on Firefox, install the
Transliterator Add-on HERE
Open the options dialog of the Transliterator Add-on, and select Arabic.
To use, go to a any text input box on a web page, and press ALT-Z (or whatever is set as the “toggle keyboard mode” shortcut in the Transliterator options), this should toggle between Arabeasy input and normal input. You should now be able to type Arabic using the ArabEasy keyboard mapping.
You can also transliterate Arabic text on any page withe the Transliterate shortcut key defined in the Add-on options, I like to use ATL-A for this, so then you just select any text or the whole page with CTRL-A, and then convert to ArabEasy with ALT-A.
You may need to restart Firefox for changes to shortcut keys to come into effect.