FontViewOK

Very useful tool for quick, visual comparison of fonts. No real, free of open alternative in this class. Somehow it reminds me tools from NirSoft - quick, light and does its job well. Producer - SoftwareOK - also has a nice collection of light, nice tools.

Pros:

• simple and light interface
• very fast
• basic functionality (which may be con as well)
• free (i.e. no ads at all)
• can show system fonts or fonts from user provided directory
• does what it is supposed to do
• active project.
• support systems up to Windows 11
• support for older, 32 bit systems
• basic management (install, delete [to bin])

Cons:

1. only side to side compare (no way to compare in place, as overlay) - could be mitigated by right click and "save as image", then eventually using e.g. Gimp to do overlay compare) 1a) bug with above for smaller sizes I get image with only lower half text visible and it forces font name/path in the saved image 1b) the mitigation could be faster if there would be an option "open in external editor" - so far there's only "open in ms paint"
2. something I miss the most and what takes one star out of my rating - lack of ability to create own (or choose predefined) font groups, like handwritting, monospace etc. - could be mitigated by creating copy of font directory and putting desired font group in single directory
3. lack of kind of more advanced features like "calculate font coverage" (to filter out fonts that doesn't have specific characters - mostly local, like żółć) known from BabelMap 3a) per above: if font is missing characters, it's using Windows font substitution, which complicates the problem of filtering out fonts we don't want
4. no way to disable (e.g. by moving to other dir) font - just delete or keep

Overall, in my case, despite all these tiny disadvantages, it's in my must-have list.