Version 46.5 works with Firefox ESR 52.5.3

Download the file, drag it onto the addons screen, confirm install prompt

https://addons.mozilla.org/firefox/downloads/file/438176/type:attachment/theme_font_size_changer-46.5-tb+fx+sm-mac.xpi?src=version-history

Make sure you have disabled automatic updates for the addon (double click it at "Add-ons Manager" screen, scroll down, select "Off" for "Automatic Updates")

Can't live without theme font size changer! Please fix it so that it works with FB and FF again! Thanks!

Alles war perfekt funktioniert nicht mit FF 55.0.3

Helpful info.. (I've been here before because of nonworking TFSC) and my old eyes need help, like a lot of peeps showing up here :)
First, I only use PC Waterfox 64bit 54ver. and I use Thunderbird 32bit 52ver. I have ALL my addon's turned off and not to update including WF and TB. I realize now, That Firefox and Thunderbird will never add some helpful font adjustments for our bad eyes :(
So,...
If you read through the reviews. You'll see some info reviews on how to download and install a non expiring version of TFSC on earlier version of FF, Waterfox, TB. I only wanted to help people because I feel their pain on not being able to see and need help and remember to turn off all updates that includes FF, TB, WF. . I still want to give props to the Author of TFSC. Thx you!
.

Great addon firefox menus are too small to see without it.

This addon shouldn't exist there should just be a firefox option to increase menu font size but there's not, and this addon filled the gaping usability design flaw left by mozilla.

But Firefox killed it. : (

In firefox's constant quest to make a crappier version with less features and capabilities every revision, they made it so this addon will no longer function for safety reasons.

Thanks Mozilla I'm safer but now I can't see the menus. >:(

good

For all those complaining about the latest version not working (aside from the developer's action and more importantly, the handcuffs imposed by Mozilla on FF 57+ which kills and prevents many add-ons from EVER working with Web Extensions) - stay with Theme Font & Size Changer version 56, available here: https://addons.mozilla.org/en-GB/firefox/addon/theme-font-size-changer/versions/ and stay with Firefox version 56.

You can lock the current version of any add-on via the Add-on Manager: click on the "More" link next to an add-on and change "Automatic Updates" to "Off".
Firefox still alerts if an update is available but doesn't automatically update it, giving you the opportunity to check the changes made/reviews BEFORE any changes get made.

the best

IWhy, oh, why do programmers insist on writing programs with such small fonts that those with poor eyesight, even when wearing glasses, CANNOT read their programs. Furthermore, these programmers, who probably use 56 inch screens, don't incorporate a way of increasing the font size.

The theme and font changer worked exceptionally well for me - but now, the lastest invention from Mozilla Firefox has left me unable to read the Firefox menu - so how can I use it.

I am now going to immediately look for a different browser where I can read the menu and hopefully will allow me to use the Theme and Font Changer add-on as I have found it an invaluable addition over the years.

cant live without this! love to see the items on the browser bars!

I COULD SEE THE WORDS

j'adore cette extension à cause de ma vue ; mais en ce moment , elle ne fonctionne plus ; pour moi c'est embêtant

I need this app and yet FF has made it so it can't be used. Mozilla needs to change its course. The full themes were incredible, the main reason why I used FF. This is a FANTASTIC app.

Great extension, I hope it not drop. If someone will help, there is a small means of partial replacement to this addon.
1. Place/Create/Add next file "userChrome.css" into "chrome" subfolder in your profile, e.g. C:\Users\usename\Appdata\Roaming\Mozilla\Firefox\Profiles\cdar87xx.default\chrome;
2. Fill userChrome.css next content, for example:
* {font-size: 10pt !important; font-family: "Roboto" !important;}
3. It means that you have this font already installed. You can set your own font-size and font-family values, ofcourse;
4. Restart FF.
Now it looks closely than I has with TFSC.

Until this stuff is fixed for newer Firefox use this hack to get font size bigger:
create userChrome.css in the profiles /chrome folder and enter

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

menubar, menubutton, menulist, menu, menuitem, textbox,
toolbar, .tab-text, tree, tooltip, sidebarheader, statusbar {
font-size: 20px !important; }

It's the EASIEST to use, even for those not so Computer savvy, such as myself! Takes you through all the areas you would like to change!!!

Mit der Version 57 von FireFox hat Mozilla definitiv die rote Linie überschritten. Der "freie" Browser schreibt mir vor, was ich an Addons installieren darf? Geht gar nicht.

Nur dank dem Addon "Theme and Font Size Changer" konnte man FireFox überhaupt benutzen ohne Augenkrebs zu bekommen. Nun wird das verunmöglicht.

Das heisst für mich klar: Ich wechsle jetzt zu Google Chrome. Schade um die Idee des freien Browsers Mozilla!

Please Please bring this one to Firefox 57
My old eyes would be forever thanfull

If your add-on is no longer working, you'll need to downgrade to the previous version:
1- Remove (uninstall) the Theme Font& Size Changer addon
2- Go to this page and download/install version 56.0
https://addons.mozilla.org/en-US/firefox/addon/theme-font-size-changer/versions/
3- To prevent the add-on from updating itself to the latest version, you'll need to disable it (note: this will also disable auto-updates for all other add-ons). Follow these steps here: https://blog.mozilla.org/addons/how-to-turn-off-add-on-updates/

I REALLY need this extension back! Please do all possible to hasten it's recovery. Thanks.