Really helps on HIDPI screen that is somewhat washed-out. Good work!

Breaks Google Calendar on my Asus tablet using Firefox 89.0

The most useful extension I have ever used. Saves constant zooming in and out of web pages to read small faint fonts. Wonderfully customisabe, easy to use and light on resources. Many thanks to very capable dev.

It's challenging reading grey font on a white background, and this is the best solution I've found so far. Looking forward to testing it out thoroughly. Curiously, the only page it hasn't worked on so far is the mozilla add ons page (https://addons.mozilla.org/en-US/firefox/addon/font-contrast-fix). Perhaps I'm doing something wrong?

This addon makes reading much easier, I appreciate it. A small improvement would be welcome: when activated, it does not affect the text of unfolded comments in livejournal.

Option panel doesn't show options ! FF 78.0.1 x64 win10 here and last version of extension

Can Someone explain what is the difference between Increase font (%) and Threshold (px)?

I finally gave in and switched to Firefox Quantum as my default browser, and am grateful to Fushko for Font Contrast. Chromium (Chrome minus Google elements) has a similar High Contrast extension, but it affects all page elements, ruining most images. This extension is well-designed, easy to configure, and -- understanding that this can be a complex feature -- I'm glad to see that the developer is very responsive to user feedback.

I could be mistaken, but I think the "Form Border" option is only available via the options button in the address bar (popup panel). It's missing when accessing the settings through the addon manager. I think I'm using the latest version of the extension. My machine runs Firefox 56.0.2 64-bit on Windows 7 64-bit platform. The issue could be with my outdated version of Firefox - which I deliberately don't want to upgrade. Aside from that, this extension is absolutely awesome! Love the toggle on/off option.

UPDATE 07/04/2020:

This is a second review unrelated to my first. I wanted to make a suggestion. In the options, the word "dims" is a little ambiguous. I wonder if you might change the text of your hover help tip for "ADVANCED MODE" to read: "Darkens text to a deeper shade of its color instead of black"? then maybe label the "BRIGHTNESS %" option below "DARKNESS %" instead? Maybe it's just me, but using "DIMS" in tandem with "BRIGHTNESS" is perplexing. Love the addon otherwise!

I trust this developer. He or she was thoughtful and communicated with users. Also, this is simple, robust work. It made text appear black instead of greyed out, like this page requires. Which is stupid. Therefore, I'd bet it's a smartphone stupidity thing.

It seems you have to click the icon on each page opened, which is fine. Firefox 71.0 64 bit.

Good extension, but needs more refinement in performance area. It freezes FF for several seconds, turns pages loading very slow. Blacken is better for now.

Great addon for blurry Windows 10, 5 stars absolutely!

Wonderful for old eyes. Dramatic increase in text darkening. Also can adjust font size, boldness, more within Firefox sourced websites. Much needed with current crop of default fine, light print operating systems.
AR
Running Android 10 on Google Pixel

I sometimes browse or read on an e-ink tablet screen, which feels nicer for my eyes especially for long form reading. Unfortunately sometimes the font uses a lighter gray color and so is harder to read even if on a white background. That's where this extension helps. It makes the page text much easier to read by bolding it among other things. Very useful on a screen type where more contrast is welcome. Thanks!