There was another review saying it doesn't automatically check for updates in FF 57, so I'm just living a review to say that it does work for me.

I've only been using this plugin a few hours in FF, but I used it for years in Chrome, so very happy to give the 5 star review.

Very useful, best addon for gmail.

Finally, found best gmail checker extension (tested on 55.0.2 64 bit)

ATM, this is the best WebExtensions Gmail checker/button. The built-in popup isn't annoying and if you really want just a button and notifier to Gmail you can just choose so.

By default this is broken in Fx57 though, because Tracking Protection enabled seems to inhibit the addon from logging in. Not sure if this is a Firefox or addon bug.

Checking it now

A lot of reviews are probably from competitors since this is the best one I've used and I've used them all.

Love you
More power

Pues eso, después de instalar este complemento, y teniendo la sesión en Gmail abierta, me pide iniciar sesión en Gmail; y después de hacerlo no ocurre nada, dado que me sigue pidiendo iniciar sesión. He desinstalado el complemento porque además no me convence el tamaño que ocupa...

it looks modern with good features, but it's not what it seams to be.
Auto login always fails.
Manually account is "forgotten" several times, very often asks for login and permission - again and again.
it looks like it does not actualize very often, i have to do it manually.
The configuration is not actualized for FIREFOX users.
Help and config only for Chrome.
simply doesn't do for what it's builded for, at least NOT in Firefox, and it's laggy very often, sometimes fast.
I cannot recommend it anymore after using it 2 Weeks.

After using another much more rudimentary add on, this well written and continually updated add on is a pleasure to use.
Don't feel the need to go into specifics as it's all in the description, suffice it to say if you use Firefox and Gmail this is a must have add on.

I have used the Gmail Checker before, but now it is broken by changed in authentication process. I have installed this app and I really comfortable with it - i find the opening pop-up windows where you can manage your accounts and mails is really super!

The best extension I have ever used to manage Gmail accounts.
Five stars for sure!

Many thanks to author. I moved on from GMailChecker https://addons.mozilla.org/en-US/firefox/addon/gmail-checker/ and want to say that CheckerPlus is a gorgeous and stunning add-on.