Список MIME-types, подлежащих сжатию:
application/atom+xml
application/javascript
application/json
application/ld+json
application/manifest+json
application/rss+xml
application/vnd.geo+json
application/vnd.ms-fontobject
application/x-font-ttf
application/x-web-app-manifest+json
application/xhtml+xml
application/xml
font/opentype
image/bmp
image/svg+xml
image/x-icon
text/css
text/plain
text/vcard
text/vnd.rim.location.xloc
text/vtt
text/x-component
text/x-cross-domain-policy
text/html
text/cache-manifest
Источник:
server-configs-nginx