Failed to decode downloaded font

In the css rule you have to add the extension of the file. This example with the deepest support possible:

@font-face {
  font-family: 'MyWebFont';
  src: url('webfont.eot'); /* IE9 Compat Modes */
  src: url('webfont.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
       url('webfont.woff2') format('woff2'), /* Super Modern Browsers */
       url('webfont.woff') format('woff'), /* Pretty Modern Browsers */
       url('webfont.ttf')  format('truetype'), /* Safari, Android, iOS */
       url('webfont.svg#svgFontName') format('svg'); /* Legacy iOS */
}

EDIT:

"Failed to decode downloaded font" means the font is corrupt, or is incomplete (missing metrics, necessary tables, naming records, a million possible things).

Sometimes this problem is caused by the font itself. Google font provides the correct font you need but if font face is necessary i use Transfonter to generate all font format.

Sometimes is the FTP client that corrupt the file (not in this case because is on local pc). Be sure to transfer file in binary and not in ASCII.

Make sure your server is sending the font files with the right mime/type.

I recently have the same problem using nginx because some font mime types are missing from its vanilla /etc/nginx/mime.types file.

I fixed the issue adding the missing mime types in the location where I needed them like this:

location /app/fonts/ {

  #Fonts dir
  alias /var/www/app/fonts/;

  #Include vanilla types
  include mime.types;

  #Missing mime types
  types  {font/truetype ttf;}
  types  {application/font-woff woff;}
  types  {application/font-woff2 woff2;}
}

You can also check this out for extending the mime.types in nginx: extending default nginx mime.types file

I had to add type="text/css" to my link-tag. I changed it from:

<link href="https://fonts.googleapis.com/css?family=Roboto+Condensed:300,400,700" rel="stylesheet">

to:

<link href="https://fonts.googleapis.com/css?family=Roboto+Condensed:300,400,700" rel="stylesheet" type="text/css">

After I changed it the error disappeared.

I experienced a similar issue in Visual Studio, which was being caused by an incorrect url() path to the font in question.

I stopped getting this error after changing (for instance):

@@font-face{
    font-family: "Example Font";
    src: url("/Fonts/ExampleFont.eot?#iefix");

to this:

@@font-face{
    font-family: "Example Font";
    src: url("../fonts/ExampleFont.eot?#iefix");