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Server Side Performance Tricks


Over time I've learned that performance is a two way street that requires good server configurations and good content management.

You should avoid using .htaccess files completely if you have access to httpd main server config file. Using .htaccess files slows down your Apache http server. Any directive that you can include in a .htaccess file is better set in a Directory block, as it will have the same effect with better performance.

Cross Origin Requests #

These rulles allow servers to work around the same-origin policy and accept resources origin

This is not without risks as it opens your server to potentially maliciously crafted resources originating from outside your domain and which you have no control over.

Generic CORS requests #

Sends the CORS headers for all resources.

  Header set Access-Control-Allow-Origin "*"

Cross-origin images #

Send the CORS header for images when browsers request it.

      SetEnvIf Origin ":" IS_CORS
      Header set Access-Control-Allow-Origin "*" env=IS_CORS

Cross-origin web fonts #

Send the CORS header for web fonts when browsers request them.

    Header set Access-Control-Allow-Origin "*"

Cross-origin resource timing #

Allow cross-origin access to the timing information for all resources.

If a resource isn't served with a Timing-Allow-Origin header that would allow its timing information to be shared with the document, some of the attributes of the PerformanceResourceTiming object will be set to zero.

  Header set Timing-Allow-Origin: "*"

Media Types #

Serve resources with the proper media types (MIME types).

Normalize Javascript to standard type per

  # Data interchange
    AddType application/atom+xml                        atom
    AddType application/json                            json map topojson
    AddType application/ld+json                         jsonld
    AddType application/rss+xml                         rss
    AddType application/vnd.geo+json                    geojson
    AddType application/xml                             rdf xml

  # JavaScript
    AddType application/javascript                      js mjs

  # Manifest files
    AddType application/manifest+json                   webmanifest
    AddType application/x-web-app-manifest+json         webapp
    AddType text/cache-manifest                         appcache

  # Media files
    AddType audio/mp4                                   f4a f4b m4a
    AddType audio/ogg                                   oga ogg opus
    AddType image/bmp                                   bmp
    AddType image/svg+xml                               svg svgz
    AddType image/webp                                  webp
    AddType video/mp4                                   f4v f4p m4v mp4
    AddType video/ogg                                   ogv
    AddType video/webm                                  webm
    AddType video/x-flv                                 flv

  # Web fonts
    AddType font/woff                                   woff
    AddType font/woff2                                  woff2
    AddType application/               eot
    AddType font/ttf                                    ttf
    AddType font/collection                             ttc
    AddType font/otf                                    otf

  # Other
    AddType application/octet-stream                    safariextz
    AddType application/x-bb-appworld                   bbaw
    AddType application/x-chrome-extension              crx
    AddType application/x-opera-extension               oex
    AddType application/x-xpinstall                     xpi
    AddType text/calendar                               ics
    AddType text/markdown                               markdown md
    AddType text/vcard                                  vcard vcf
    AddType text/vnd.rim.location.xloc                  xloc
    AddType text/vtt                                    vtt
    AddType text/x-component                            htc

Character encodings #

Serve all resources labeled as text/html or text/plain with the media type charset parameter set to UTF-8.

AddDefaultCharset utf-8

Serve the following file types with the media type charset parameter set to UTF-8.

AddCharset utf-8 .atom \
  .bbaw \
  .css \
  .geojson \
  .ics \
  .js \
  .json \
  .jsonld \
  .manifest \
  .markdown \
  .md \
  .mjs \
  .rdf \
  .rss \
  .topojson \
  .vtt \
  .webapp \
  .webmanifest \
  .xloc \

Rewrite Engine #

  1. Turn on the rewrite engine (this is necessary in order for the RewriteRule directives to work).

  2. Enable the FollowSymLinks option if it isn't already.

  3. If your web host doesn't allow the FollowSymlinks option, you need to comment it out or remove it, and then uncomment the Options +SymLinksIfOwnerMatch line (4), but be aware of the performance impact.

  4. Some cloud hosting services will require you set RewriteBase.

  5. Depending on how your server is set up, you may also need to use the RewriteOptions directive to enable some options for the rewrite engine.

  6. Set %{ENV:PROTO} variable, to allow rewrites to redirect with the appropriate schema automatically (http or https).

    RewriteEngine On # (1)
    Options +FollowSymlinks # (2)
    # Options +SymLinksIfOwnerMatch # (3) (4)
    # RewriteBase /
    # RewriteOptions  # (5)
    RewriteCond %{HTTPS} =on  # (6)

    RewriteRule ^ - [env=proto:https]
    RewriteCond %{HTTPS} !=on
    RewriteRule ^ - [env=proto:http]

Forcing https #

Redirect from the http:// to the https:// version of the URL.

   RewriteEngine On
   RewriteCond %{HTTPS} !=on
   RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]

Content Security Policy (CSP) #

Mitigate the risk of cross-site scripting and other content-injection attacks.

This can be done by setting a Content Security Policy which whitelists trusted sources of content for your website.

The example header below allows ONLY scripts that are loaded from the current website's origin (no inline scripts, no CDN, etc). That almost certainly won't work as-is for your website!

To make things easier, you can use an online CSP header generator such as

mod_headers cannot match based on the content-type, however, the `Content-Security-Policy` response header should be send only for HTML documents and not for the other resources.

  Header set Content-Security-Policy "script-src 'self'; object-src 'self'"

      Header unset Content-Security-Policy


File access #

Block access to directories without a default document.

You should leave the following uncommented, as you shouldn't allow anyone to surf through every directory on your server (which may include rather private places such as the CMS's directories).

    Options -Indexes

Block access to all hidden files and directories with the exception of the visible content from within the /.well-known/ hidden directory.

These types of files usually contain user preferences or the preserved state of an utility and can include rather private places like, for example, the .git or .svn directories.

The /.well-known/ directory represents the standard (RFC 5785) path prefix for "well-known locations" (e.g.: /.well-known/manifest.json, /.well-known/keybase.txt), and therefore, access to its visible content should not be blocked.

    RewriteEngine On
    RewriteCond %{REQUEST_URI} "!(^|/)\.well-known/([^./]+./?)+$" [NC]
    RewriteCond %{SCRIPT_FILENAME} -d [OR]
    RewriteCond %{SCRIPT_FILENAME} -f
    RewriteRule "(^|/)\." - [F]

Block access to files that can expose sensitive information.

By default, block access to backup and source files that may be left by some text editors and can pose a security risk when anyone has access to them.


(!) Update the <filesmatch> regular expression from below to include any files that might end up on your production server and can expose sensitive information about your website. These files may include: configuration files, files that contain metadata about the project (e.g.: project dependencies), build scripts, etc.

    # Apache < 2.3
        Order allow,deny
        Deny from all
        Satisfy All

    # Apache ≥ 2.3
        Require all denied

HTTP Strict Transport Security (HSTS) #

Force client-side SSL redirection. If a user types in their browser, even if the server redirects them to the secure version of the website, that still leaves a window of opportunity (the initial HTTP connection) for an attacker to downgrade or redirect the request. The following header ensures that browsers will ONLY connect to your server via HTTPS, regardless of what the users type in the browser's address bar.

(!) Remove the includeSubDomains optional directive if the website's subdomains are not using HTTPS.

  Header always set Strict-Transport-Security "max-age=16070400; includeSubDomains"

Reducing MIME type security risks #

Prevent some browsers from MIME-sniffing the response.

This reduces exposure to drive-by download attacks and cross-origin data leaks, and should be left uncommented, especially if the server is serving user-uploaded content or content that could potentially be treated as executable by the browser.

    Header set X-Content-Type-Options "nosniff"

Reflected Cross-Site Scripting (XSS) attacks #

  1. Try to re-enable the cross-site scripting (XSS) filter built into most web browsers.

    • The filter is usually enabled by default, but in some cases it may be disabled by the user. However, in Internet Explorer for example, it can be re-enabled just by sending the X-XSS-Protection header with the value of 1.
  2. Prevent web browsers from rendering the web page if a potential reflected (a.k.a non-persistent) XSS attack is detected by the filter.

    • By default, if the filter is enabled and browsers detect a reflected XSS attack,they will attempt to block the attack by making the smallest possible modifications to the returned web page.
    • Unfortunately, in some browsers (e.g.: Internet Explorer), this default behavior may allow the XSS filter to be exploited, thereby, it's better to inform browsers to prevent the rendering of the page altogether, instead of attempting to modify it [IE's XSS Filter Creates XSS Vulnerabilities] (

(!) Do not rely on the XSS filter to prevent XSS attacks! Ensure that you are taking all possible measures to prevent XSS attacks, the most obvious being: validating and sanitizing your website's inputs.


mod_headers cannot match based on the content-type, however, the X-XSS-Protection response header should be send only for HTML documents and not for the other resources.

  #                           (1)    (2)
  Header set X-XSS-Protection "1; mode=block"

      Header unset X-XSS-Protection

Server-side technology information #

Remove the X-Powered-By response header that:

  • is set by some frameworks and server-side languages (e.g.: ASP.NET, PHP), and its value contains information about them (e.g.: their name, version number)
  • doesn't provide any value to users, contributes to header bloat, and in some cases, the information it provides can expose vulnerabilities

(!) If you can, you should disable the X-Powered-By header from the language / framework level (e.g.: for PHP, you can do that by settingexpose_php = off in php.ini)


    Header unset X-Powered-By

Server software information #

Prevent Apache from adding a trailing footer line containing information about the server to the server-generated documents (e.g.: error messages, directory listings, etc.)

ServerSignature Off

Prevent Apache from sending in the Server response header its exact version number, the description of the generic OS-type or information about its compiled-in modules.

(!) The ServerTokens directive will only work in the main server configuration file, so don't try to enable it in the .htaccess file!

#ServerTokens Prod

Compression #

Force compression for mangled Accept-Encoding request headers.

       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

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

(!) For Apache versions below version 2.3.7 you don't need to enable mod_filter and can remove the <ifmodule mod_filter.c>and </ifmodule> lines as AddOutputFilterByType is still in the core directives.

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/" \
    "application/x-font-ttf" \
    "application/x-javascript" \
    "application/x-web-app-manifest+json" \
    "application/xhtml+xml" \
    "application/xml" \
    "font/collection" \
    "font/eot" \
    "font/opentype" \
    "font/otf" \
    "font/ttf" \
    "image/bmp" \
    "image/svg+xml" \
    "image/" \
    "image/x-icon" \
    "text/cache-manifest" \
    "text/calendar" \
    "text/css" \
    "text/html" \
    "text/javascript" \
    "text/plain" \
    "text/markdown" \
    "text/vcard" \
    "text/vnd.rim.location.xloc" \
    "text/vtt" \
    "text/x-component" \
    "text/x-cross-domain-policy" \

Map the following filename extensions to the specified encoding type in order to make Apache serve the file types with the appropriate Content-Encoding response header(do note that this will NOT make Apache compress them!).

If these file types would be served without an appropriate Content-Enable 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.


      AddEncoding gzip              svgz

ETags #

Remove ETags as resources are sent with far-future expires headers.

# `FileETag None` doesn't work in all cases.

  Header unset ETag

FileETag None

Expires headers #

Serve resources with far-future expires headers.

(!) If you don't control versioning with filename-based cache busting, you should consider lowering the cache times to something like one week.

  ExpiresActive                             on
  ExpiresDefault                            "access plus 1 month"

  ExpiresByType text/css                    "access plus 1 year"

# Data interchange
  ExpiresByType application/atom+xml        "access plus 1 hour"
  ExpiresByType application/rdf+xml         "access plus 1 hour"
  ExpiresByType application/rss+xml         "access plus 1 hour"
  ExpiresByType application/json            "access plus 0 seconds"
  ExpiresByType application/ld+json         "access plus 0 seconds"
  ExpiresByType application/schema+json     "access plus 0 seconds"
  ExpiresByType application/vnd.geo+json    "access plus 0 seconds"
  ExpiresByType application/xml             "access plus 0 seconds"
  ExpiresByType text/calendar               "access plus 0 seconds"
  ExpiresByType text/xml                    "access plus 0 seconds"

# Favicon (cannot be renamed!) and cursor images
  ExpiresByType image/    "access plus 1 week"
  ExpiresByType image/x-icon                "access plus 1 week"

  ExpiresByType text/html                   "access plus 0 seconds"

# JavaScript
  ExpiresByType application/javascript      "access plus 1 year"
  ExpiresByType application/x-javascript    "access plus 1 year"
  ExpiresByType text/javascript             "access plus 1 year"

# Manifest files
  ExpiresByType application/manifest+json   "access plus 1 week"
  ExpiresByType application/x-web-app-manifest+json   "access plus 0 seconds"
  ExpiresByType text/cache-manifest         "access plus 0 seconds"

# Markdown
  ExpiresByType text/markdown               "access plus 0 seconds"

# Media files
  ExpiresByType audio/ogg                   "access plus 1 month"
  ExpiresByType image/bmp                   "access plus 1 month"
  ExpiresByType image/gif                   "access plus 1 month"
  ExpiresByType image/jpeg                  "access plus 1 month"
  ExpiresByType image/png                   "access plus 1 month"
  ExpiresByType image/svg+xml               "access plus 1 month"
  ExpiresByType image/webp                  "access plus 1 month"
  ExpiresByType video/mp4                   "access plus 1 month"
  ExpiresByType video/ogg                   "access plus 1 month"
  ExpiresByType video/webm                  "access plus 1 month"

# Web fonts
  # Collection
  ExpiresByType font/collection             "access plus 1 month"
  # Embedded OpenType (EOT)
  ExpiresByType application/  "access plus 1 month"
  ExpiresByType font/eot                    "access plus 1 month"
  # OpenType
  ExpiresByType font/opentype               "access plus 1 month"
  ExpiresByType font/otf                    "access plus 1 month"
  # TrueType
  ExpiresByType application/x-font-ttf      "access plus 1 month"
  ExpiresByType font/ttf                    "access plus 1 month"
  # Web Open Font Format (WOFF) 1.0
  ExpiresByType application/font-woff       "access plus 1 month"
  ExpiresByType application/x-font-woff     "access plus 1 month"
  ExpiresByType font/woff                   "access plus 1 month"
  # Web Open Font Format (WOFF) 2.0
  ExpiresByType application/font-woff2      "access plus 1 month"
  ExpiresByType font/woff2                  "access plus 1 month"

# Other
  ExpiresByType text/x-cross-domain-policy  "access plus 1 week"

Filename-based cache busting #

If you're not using a build process to manage your filename version revving, you might want to consider enabling the following directives to route all requests such as /style.12345.css to /style.css.

To understand why this is important and even a better solution than using something like *.css?v231, please see: Revving Filenames: don’t use querystring

  RewriteEngine On
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteRule ^(.+)\.(\d+)\.(bmp|css|cur|gif|ico|jpe?g|m?js|png|svgz?|webp|webmanifest)$ $1.$3 [L]

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