Is it possible to directly replace a system font with a revised font?

[beachboybogart]

I'm a novice and haven't quite figured out the Project thing yet. But I am wondering if it possible to directly save or replace a system font with a revision I've made using FontCreator. (I've changed the number "1" in a font to make it larger and easier to read on screen.)

Sorry if this has been asked, but several searches produced no associated results. ... Mike

[Erwin Denissen]

A system font is most likely locked by Windows and therefor can't be easily replaced. There is obviously a reason why it isn't easy, as it can really mess up your system.

I haven't tried it myself, but it seems people have managed to do it:
How to change the default system font on Windows 10

Good luck, and don't blame us if it ruins your system.

[PJMiller]

I recently did this, using a similar method to the one in the guide pointed to by Erwin, replacing the system font with my Cadman font. It had mixed results and eventually I changed things back.

Replacing the system font is all very well but it became apparent that there are many places where Windows 10 assumes the size and spacing of the system font so doesn't bother to check. This is just sloppy programming by Microsoft but I suppose making these assumptions might speed things up very slightly. In Windows 7 you could change the font being used for many UI elements so it adjusted everything to fit the font being used.

This means that when you substitute a different set of fonts how well they work will depend on how similar they are to the Segoe UI family of fonts. Not similar in terms of the design of the characters but similar in terms of the size of the characters (units per em), Line gap, Win Ascent, Win Descent and other metrics associated with the font.

If you are going to do this then make a backup of the Segoe UI family of system fonts before doing anything, trust me on this, when you end up wanting to change things back you will need this.

[beachboybogart]

Thanks for the responses.

I see my question was poorly worded. I should have said "installed" font. My apologies. This is about process.
A user can open an installed font, but cannot save that font directly. It has to be saved as a Project, or exported, as far as I can tell.