Combination of underscore and dash incorrectly redirects

[jericjan]

I'll have a URL like this: https://api.memegen.link/images/vince/a/_.b/c-d.png

But then it just collapses and turn into this: https://api.memegen.link/images/vince/a.b/c_d.png

These work fine tho: https://api.memegen.link/images/vince/a/.b/c-d.png https://api.memegen.link/images/vince/a/_b/c-d.png

What is this behavior? Is it just how the browser handles URLs or is it something on memegen's side?