This addon is useless when in the settings I made so that I had the language of Poland, so it automatically put me on the United States so far it's the bottom maybe if something changes for the better I can pick up but now I categorically advise anyone to download : - (
I like this program. I like the way I can change the voices on the fly. I use Firefox 60 and keep the Add-ons Manager open. I then highlight the text, have it read out to me. Go to the Add-ons manager, change the voice and highlight another part of the text - it's great. I like the way the voice keeps talking after the end of a line of text rather than pausing after each line which other programs do. I also use it to read out large sections of scanned text by saving them to a text file, renaming it to html and then opening it to Firefox (or whatever). If you want to follow the text as it is read, rememer to add the html code to create a new line or for a new paragraph. I like this program and would be interested in it's development for reading on line pdf documents etc.
Working good for me so far and I like the voice, not so robotic. Digging it. Though I'm seeing that it doesn't work on every page and I don't know why yet... Also, much like xdronetek said, I only have the female voice and no option to change it. I'm on Firefox 61 and I use a PC Windows 7. It would be nice to try out other voices.
Which website are you trying it on? I just checked it on Firefox 54.0.1 and it seems to be working fine. Some websites do not allow add-ons to access their content. I tried it on https://en.wikipedia.org/wiki/Main_Page and I know that https://addons.mozilla.org is one of the websites that do not allow content access.
Thank you for your kind words. Do you know which version of Firefox and what operating system you were testing it on? I just tested it again with a few different configurations and it seems to be working fine with changing gender and language of the voice. Also, what gender and language did you test it with? If you prefer, you can send it over email at firstname.lastname@example.org