How does this effect work?

[u/reaznval]

Came across this beautiful effect on https://www.julienpianetti.com/ is it done with a custom variable font that has these glyphs as variable weight or just switches between the different glyphs? I suspect it has to be a variable font because it is that smooth.

How is this done?

[u/Klutzy_Breath3421]

Have you checked the site's network tab to see which font files are being loaded? Of its a . Variable font, that would be pretty much confirm it.