It does a great job on website text. However it does not increase the font size of the toolbars: bookmark tool bar, menu tool bar and there consequent texts. So I am still peeering at these (for me) tiny names and texts. I am 74 years old and my eyesight is not as flexible any longer. I treied resetting the fonts in Firefox options as well as in Windows settings. None of them address these situations. Thank you for trying.
Cheers.
R.

(5-star) Very useful addon to deal with websites that use too little contrast, set text sizes that are too small, etc. Still has trouble with text-shadow though.

UPDATE 2019-04-10: downgrading it to 2-star for now. It is causing frequent freezes which is very annoying when typing in Firefox.

Disable is not reliable.

For example:

1. visit https://www.logilab.org/

2. use the Legibility icon to disable Legibility

3. close the tab

4. open a new tab

5. visit https://www.logilab.org/

Expected:

- no effect of Legibility

Actual result:

- effects of Legibility

Workaround:

- enable
- disable

– but the workaround is not persistent.

I first found this problem with Legibility for Firefox, added to Waterfox 56.2.0.31_7 on FreeBSD-CURRENT.

Reproducible with Legibility on Chromium 65.0.3325.181 (Official Build) (64-bit) on FreeBSD-CURRENT.

2.5 stars. This extension is the only one of it's kind that works at all for the current version of Firefox, however, the developer should compare it to Chrome's extension "Font Rendering Enhancer". There, there is only one setting. The contrast is increased without distortion and all colors are kept including the color of links (it seems to me that the extension causes Chrome to render all the text on a page twice; first where it belongs and then again shifted to the right less than one pixel, and it's adjustable). On the other hand, this extension for Firefox, known as Legibility is awkward and at best will make colored text monochrome (as well as text intended to be grey). But, since it is the only practical solution available for Firefox text, I'm giving it 2.5 stars.