Rated 5 out of 5 stars

A great add-on for anyone who needs to enter non-ASCII characters.

Have used Zombie Keys for ~9 years. Initially chose it because of MS-Office compatibility.

Very happy with how it works and with the level of support and enhancement over the years. Updates are very timely, to keep up with new versions of TB and FF.

Also very happy that it seems to work in any input field in FF or TB, including email composition, search engine input, HTML form input in Firefox (such as Google Maps input field), and so on.

This review is for a previous version of the add-on (2.19). 

... as once Firefox forces MultiProcess windows, we cannot easily inject content into the browser anymore. Which means there will have to be a major rewrite of that part of the addon. But I still intend to support the "privileged parts" which also includes things like search boxes in Thunderbird and of course the Composition Window. The other problem on the horizon will be the deprecation of XUL addons (Firefox 57) I am hoping that I can still keep Zombie Keys alive and offer all the functionality then. If not, then there is always the Pale Moon fork!