Font files are not loading with ASP.NET Bundles

Great answer above.

An alternative - if for some reason the above didn't work for you - would be to change how the @font-face src property references the 'Fonts' folder. '../'-ing doesn't work very well for bundling so reference directly from the site root folder instead. Assumung the 'Fonts' folder is one down from the root, change this:

@font-face {
  src: url('../Fonts/ProximaNova/ProximaNova-Bold.otf') format('opentype');
}

To this:

@font-face {
  src: url('/Fonts/ProximaNova/ProximaNova-Bold.otf') format('opentype');
}

You will retrieve the same results when the site is ran in debug mode too.

Well, I think the problem is with your font location. I'm assuming that the bundled css virtual location /BundleStyles/css doesn't actually exist. and if your folders structure like below

Content > Font

Content > style

If this is true, then try this

change /BundleStyles/css to /Content/css

<link href="/Content/css?v=pANk2exqBfQj5bGLJtVBW3Nf2cXFdq5J3hj5dsVW3u01" rel="stylesheet"/>

and reference your font like this

src: url('Fonts/ProximaNova/ProximaNova-Bold.otf')

in this case your font will be loaded relative to the "css" file which is located inside the content folder which also contains the "fonts" folder

If what I assumed is incorrect please show us how you structured your files

I think CssRewriteUrlTransform might be the way to go:

https://msdn.microsoft.com/en-us/library/system.web.optimization.cssrewriteurltransform(v=vs.110).aspx

Used like so:

.Include("~/Content/bootstrap-cosmo.min.css", new CssRewriteUrlTransform())

Worked for me.