Enable Compression in HTACCESS

gistfile1.txt

# ------------------------------------------------------------------------------
# | Compression                                                                |
# ------------------------------------------------------------------------------

<IfModule mod_deflate.c>

    # Force compression for mangled headers.
    # https://developer.yahoo.com/blogs/ydn/pushing-beyond-gzipping-25601.html

    <IfModule mod_setenvif.c>
        <IfModule mod_headers.c>
            SetEnvIfNoCase ^(Accept-EncodXng|X-cept-Encoding|X{15}|~{15}|-{15})$ ^((gzip|deflate)\s*,?\s*)+|[X~-]{4,13}$ HAVE_Accept-Encoding
            RequestHeader append Accept-Encoding "gzip,deflate" env=HAVE_Accept-Encoding
        </IfModule>
    </IfModule>

    # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    # Map certain file types to the specified encoding type in order to
    # make Apache serve them with the appropriate `Content-Encoding` HTTP
    # response header (this will NOT make Apache compress them!).

    # If the following file types wouldn't be served without the appropriate
    # `Content-Enable` HTTP response header, client applications (e.g.:
    # browsers) wouldn't know that they first need to uncompress the response,
    # and thus, wouldn't be able to understand the content.

    # http://httpd.apache.org/docs/current/mod/mod_mime.html#addencoding

    <IfModule mod_mime.c>
        AddEncoding gzip              svgz
    </IfModule>

    # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    # Compress all output labeled with one of the following media types.

    # IMPORTANT: For Apache versions below 2.3.7 you don't need to enable
    # `mod_filter` and can remove the `<IfModule mod_filter.c>` & `</IfModule>`
    # lines as `AddOutputFilterByType` is still in the core directives.

    <IfModule mod_filter.c>
        AddOutputFilterByType DEFLATE "application/atom+xml" \
                                      "application/javascript" \
                                      "application/json" \
                                      "application/ld+json" \
                                      "application/manifest+json" \
                                      "application/rdf+xml" \
                                      "application/rss+xml" \
                                      "application/schema+json" \
                                      "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/svg+xml" \
                                      "image/x-icon" \
                                      "text/cache-manifest" \
                                      "text/css" \
                                      "text/html" \
                                      "text/javascript" \
                                      "text/plain" \
                                      "text/vtt" \
                                      "text/x-component" \
                                      "text/xml"
    </IfModule>

</IfModule>

Add it AFTER the content already existent in your .htaccess file at your WordPress root folder.