Mono font has ligatures (fi, fl, ff, ffi, ffl) that are only 1 character wide

[charredUtensil]

This is true at least for the version currently on Google Fonts:

https://fonts.google.com/specimen/Overpass+Mono?query=overpass&preview.text=I%20offer%20fine%20affluent%20foxes%20no%20affixed%20fleas.&preview.text_type=custom

[jiridanek]

From the user's point of view, you can tell your application to not use ligatures, using fontconfig, as described in https://wiki.archlinux.org/title/Font_configuration/Examples#Disable_ligatures_for_monospaced_fonts. That wiki says that Firefox does not respect this setting ;(

On the web, you can direct the browser using CSS, https://developer.mozilla.org/en-US/docs/Web/CSS/font-variant-ligatures

JetBrains Mono ships a NL (non-ligature) versions of the .ttf files. Maybe that's a worthwhile route to take, for user convenience. https://stackoverflow.com/questions/62195642/what-the-difference-between-jetbrains-mono-and-jetbrains-mono-nl

[Scemist]

I noticed this, it really happens. For 'fi' and 'fl' mainly, that contains many words like 'file' is really weird.

[charredUtensil]

This is still a bug, even if it can be disabled under certain circumstances. I cannot think of a single reason anyone would want these ligatures in a monospace font.

Other monospace "code" fonts that use ligatures tend to maintain the original width of characters. JetBrains Mono also doesn't have these typographic ligatures despite having the code ones.

[jiridanek]

The https://github.com/RedHatOfficial/RedHatFont monospace variant does not suffer from this bug

https://fonts.google.com/specimen/Red+Hat+Mono?selection.family=Chathura&sidebar.open=true&preview.text=Neffnukala,%20ffikana&preview.text_type=custom

[Nagidrop]

Nerd Fonts has patched Overpass Mono with the fi, fl, and ldot ligatures removed to keep it truly monospaced. You can download it from their website