doc/https_support.html - incubator-pagespeed-website - Git at Google

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 <html>
   <head>
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <title>PageSpeed HTTPS Support</title>
     <link rel="stylesheet" href="doc.css">
   </head>
   <body>
 <!--#include virtual="_header.html" -->


   <div id=content>
 <h1>PageSpeed HTTPS Support</h1>
     <p class="note">
       As of version 1.10 HTTPS fetching (<code>FetchHttps</code>) is enabled by
       default, and PageSpeed no longer requires additional configuration to
       fetch and optimize resources over https.  The alternatives described
       below, however, are more efficient in situations where they apply.
     </p>

     <p>
       PageSpeed supports sites that serve content through https. There are
       several mechanisms through which PageSpeed can be configured to fully
       optimize sites served under https:
     </p>
     <ul>
       <li>Use <code>MapOriginDomain</code> to
           <a href="https_support#map_the_origin">map the https domain to an http
           domain</a>.</li>
       <li>Use <code>LoadFromFile</code> to
           <a href="https_support#load_from_file">map a
           locally available directory to the https domain</a>.</li>
       <li>Use <code>FetchHttps</code> to <a href="https_support#https_fetch"
           >directly fetch HTTPS resources</a> (On by default since 1.10).</li>
     </ul>

     <p>
       The first two mechanisms can both be used on the same server, but they
       must be used for different domains, for example:
     </p>

     <dl>
       <dt>Apache:<dd><pre class="prettyprint"
          >  ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
   ModPagespeedLoadFromFile "https://static.example.com" "/var/www/example/static/"</pre>
       </dd></dt>
       <dt>Nginx:<dd><pre class="prettyprint"
          >  pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
   pagespeed LoadFromFile "https://static.example.com" "/var/www/example/static/";</pre>
     </dl>

     <p>
       Even without configuring any of these options, PageSpeed
       rewrites HTML documents requested via https. PageSpeed is able to
       serve these documents because the server passes the HTML document through
       all its output filters, including *_pagespeed. But by default,
       PageSpeed will only rewrite non-HTML resources which are served
       via http. Due to the complexity and security required to manage client
       SSL certificates, PageSpeed requires the server administrator to
       explicitly enable https fetching.
     </p>

     <p>
       The configuration options mentioned above are intended to help
       optimize sites with HTTPS resources. Fetching https resource URLs
       using http should be used only in installations where using http is
       safe, such as where the server running PageSpeed is a
       front-end to other back-end systems with private communications and
       mutual trust between them.
     </p>

     <h2 id="map_the_origin">Map the origin domain</h2>

     <p>
       Https resource URLs can be fetched by mapping them to a non-https origin
       domain as described in
       <a href="domains#mapping_origin">Mapping Origin Domains</a>:
     </p>
     <dl>
       <dt>Apache:<dd>
 <pre class="prettyprint">
   ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
 </pre>
       </dd></dt>
       <dt>Nginx:<dd>
 <pre class="prettyprint">
   pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
 </pre>
       </dd></dt>
     </dl>

     <p>
       This allows the server to accept https requests for
       <code>www.example.com</code> while fetching resources for it from the
       <code>localhost</code> http server, which could be the same Apache process or a
       different server process. All fetched resources will be optimized as usual.  As
       many <code>MapOriginDomain</code> directives can be used as is required as long
       as https is only used on the second domain.
     </p>

     <h2 id="load_from_file">Load static files from disk</h2>

     <p>
       Https resource URLs can be served from static files using the
       <a href="domains#ModPagespeedLoadFromFile">LoadFromFile</a> directive:
     </p>

     <dl>
       <dt>Apache:<dd><pre class="prettyprint"
                           >ModPagespeedLoadFromFile "https://www.example.com" "/var/www/example/static/";</pre>
           <dt>Nginx:<dd><pre class="prettyprint"
                              >pagespeed LoadFromFile "https://www.example.com" "/var/www/example/static/";</pre>
     </dl>

     <h2 id="https_fetch">Fetch HTTPS resources directly</h2>
     <p>
       HTTPS fetching is built in and is enabled by default as of 1.10.33.0.
       To turn the feature off, set <code>FetchHttps</code> to
       <code>disable</code>:
     </p>

       <dl>
         <dt>Apache:<dd>
 <pre class="prettyprint">
   ModPagespeedFetchHttps enable
 </pre>
       </dd></dt>
       <dt>Nginx:<dd>
 <pre class="prettyprint">
   pagespeed FetchHttps enable;
 </pre>
       </dd></dt>
     </dl>
     <p>
       You may set multiple options, separated with a comma.  For example, to
       test a configuration with a self-signed certificate you could do:
     </p>

       <dl>
         <dt>Apache:<dd>
 <pre class="prettyprint">
   ModPagespeedFetchHttps enable,allow_self_signed
 </pre>
       </dd></dt>
       <dt>Nginx:<dd>
 <pre class="prettyprint">
   pagespeed FetchHttps enable,allow_self_signed;
 </pre>
       </dd></dt>
     </dl>

     <p>
       The available options are
       <ul>
         <li><code>enable</code></li>
         <li><code>disable</code></li>
         <li><code>allow_self_signed</code></li>
         <li><code>allow_unknown_certificate_authority</code></li>
         <li><code>allow_certificate_not_yet_valid</code></li>
       </ul>
     </p>


     <h3 id="configuring_ssl_certificates">Configuring SSL Certificates</h3>

     <p>
       Acting as an HTTPS client, PageSpeed must be configured to point to a
       directory identifying trusted
       <a href="http://en.wikipedia.org/wiki/Certificate_authority"
          >Certificate Authorities</a> (not SSL keys for your domain).  These settings will be automatically
       applied to configuration files for new binary installations on Debian,
       Ubuntu, and CentOS systems.  Upgrades, source-installs, and other
       distributions may require manual configuration updates to identify the
       proper location.</p>

       <dl>
         <dt>Apache:<dd>
 <pre class="prettyprint">
   # Certificate Authorities directory, not your domain SSL keys
   ModPagespeedSslCertDirectory directory
   # Web Server's HTTPS client SSL key, not your domain SSL keys
   ModPagespeedSslCertFile file
 </pre>
       </dd></dt>
       <dt>Nginx:<dd>
 <pre class="prettyprint">
   pagespeed SslCertDirectory directory;
   pagespeed SslCertFile file;
 </pre>
       </dd></dt>
     </dl>

     <p>
       The default directory for Debian-based systems
       is <code>/etc/ssl/certs</code>, and there is no certificate file
       setting.  On CentOS-based systems, the default directory
       is <code>/etc/pki/tls/certs</code> and default file
       is <code>/etc/pki/tls/cert.pem</code>.</p>

     <p>
       These directive cannot be used
       in <a href="configuration#htaccess"><code>.htaccess</code> files
         or <code>&lt;Directory&gt;</code></a> scopes.
     </p>

     <h2 id="rewrite_domains">Rewrite domains</h2>

     <p>
       Rewritten resources can have their https domain rewritten if required
       for the reasons described in <a href="domains#mapping_rewrite">Mapping Rewrite
         Domains</a>:
     </p>

     <dl>
       <dt>Apache:<dd><pre class="prettyprint"
          >  ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
   ModPagespeedMapRewriteDomain "https://example.cdn.com" "https://www.example.com"</pre>
       </dd></dt>
       <dt>Nginx:<dd><pre class="prettyprint"
          >  pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
   pagespeed MapRewriteDomain "https://example.cdn.com" "https://www.example.com";</pre>
       </dd></dt>
     </dl>

     <h2 id="shard_domains">Shard domains</h2>

     <p>
       Rewritten resources can have their https domain sharded if required
       for the reasons described in <a href="domains#shard">Sharding Domains</a>:
     </p>

     <dl>
       <dt>Apache:<dd><pre class="prettyprint"
          >  ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
   ModPagespeedShardDomain "https://www.example.com" \
                           "https://example1.cdn.com,https://example2.cdn.com"</pre>
       </dd></dt>
       <dt>Nginx:<dd><pre class="prettyprint"
          >  pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
   pagespeed ShardDomain "https://www.example.com"
                         "https://example1.cdn.com,https://example2.cdn.com";</pre>
       </dd></dt>
     </dl>

     <h2 id="RespectXForwardedProto">Respecting X-Forwarded-Proto</h2>
     <p>
       If you are running behind a load-balancer or other front-end that
       terminates the HTTPS connection and makes an HTTP subrequest to your
       server running PageSpeed, it will not know that the original URL was
       HTTPS and so it will rewrite subresources with <code>http://</code> URLs.
       For PageSpeed to operate correctly, it needs to know what
       the originally requested URL was. If your front-end sends
       <code>X-Forwarded-Proto</code> headers (as, for example,
       <a href="https://forums.aws.amazon.com/ann.jspa?annID=805">AWS Elastic
         Load Balancer does</a>) then you can tell PageSpeed to
       respect that header with:
     </p>
     <dl>
       <dt>Apache:<dd><pre class="prettyprint"
                           >  ModPagespeedRespectXForwardedProto on</pre>
       <dt>Nginx:<dd><pre class="prettyprint"
                           >  pagespeed RespectXForwardedProto on;</pre>
     </dl>
     <p>
       This will correctly rewrite your subresources with <code>https://</code>
       URLs and thus avoid mixed content warnings. Note, that you should only
       enable this option if you are behind a load-balancer that will set this
       header, otherwise your users will be able to set the protocol
       PageSpeed uses to interpret the request. Also, note that by default
       PageSpeed will loop back to the inbound ip/port for fetching resources
       on behalf of a html response using http(s). When X-Forwarded-Proto is in
       effect and the protocol is changed in front of the PageSpeed-enabled server,
       a mismatch may arise when performing loopback fetches, leading up to fetching
       failures. Explicitly authorizing the domain used to fetch resources will
       resolve this problem, because doing so allows the loopback fetching mechanism
       to be bypassed.
     </p>

     <p>
       This directive cannot be used
       in <a href="configuration#htaccess"><code>.htaccess</code> files
         or <code>&lt;Directory&gt;</code></a> scopes.
     </p>

     <h2 id="risks">Risks</h2>
     <p>
       As discussed above, using http to fetch https resources URLs should only be
       used when communication between the front-end and back-end servers is secure
       as otherwise the benefits of using https in the first place are lost.  When
       fetching by HTTPS, <a
       href="https://boringssl.googlesource.com/boringssl/">BoringSSL</a>
       is used to authenticate the fetches.  We bundle a copy of BoringSSL, which
       means that when security vulnerabilities are discovered that affect our usage
       we need to release updated versions of PageSpeed with the fixed BoringSSL
       library.
     </p>

     <h2 id="h2_configuration">HTTP/2-specific configuration</h2>
     <p>
       It's possible to tell PageSpeed to use a different configuration for
       clients using the HTTP/2 protocol than for clients using HTTP/1.  You can
       configure this with the <code>&lt;If&gt;</code> construct in Apache and
       with script variables in Nginx.
     </p>
     <h3 id="h2_configuration_apache">Apache Version</h3>
     <p class="note">Note: Versions older than 1.12.34.1 provided
       a <code>&lt;ModPagespeedIf&gt;</code> construct.  This is no longer supported, but
       configuration inside <code>&lt;ModPagespeedIf !spdy&gt;</code> blocks will be applied
       unconditionally for backwards compatibility.</p>

     <p>mod_http2 in Apache &ge; 2.4.19 provides an HTTP2 variable that can be used with the
       server's <code>&lt;If&gt;</code> construct to provide a different configuration for
       HTTP2 sessions. For example, one may want to disable some filters in such sessions, and only
       enable sharding in HTTP/1:
 <pre class="prettyprint">
 &lt;If "%{HTTP2} == 'on'"&gt;
   ModPagespeedDisableFilters filter1,filter2
 &lt;/If&gt;
 &lt;Else&gt;
   ModPagespeedShardDomain https://www.example.com https://example1.cdn.com,https://example2.cdn.com
 &lt;/Else&gt;</pre>

     <p>
       Note that this only covers requests terminated by mod_http2 on the Apache server itself.
       If an earlier proxy terminates HTTP/2, you may need to have it set a custom header,
       and test it using the <code>req</code> function.
     </p>

     <h3 id="h2_configuration_nginx">Nginx Version</h3>
     <p class="note"><strong>Note: New feature as of 1.10.33.0</strong></p>
 <pre class="prettyprint">
 http {
   pagespeed ProcessScriptVariables on;
   server {
     set $disable_filters "";
     set $domain_shards "shard1,shard2,shard3..."

     if ($http2) {
       set $disable_filters "filter1,filter2";
       set $domain_shards "";
     }
     pagespeed DisableFilters "$disable_filters";
     pagespeed ShardDomain domain_to_shard "$domain_shards";
   }
 }</pre>
      <p>
       The <code>$http2</code> variable is defined by
       the <a href="http://nginx.org/en/docs/http/ngx_http_v2_module.html"
       ><code>ngx_http_v2_module</a></code>, and will be non-empty on any
       connection over HTTP/2.
     </p>
     <p>
       If the connection is terminated on another server
       the <code>$http2</code> variable won't be available.  In that case, you
       can have the other server add a header for HTTP/2 connections
       like <code>X-ConnectionIsHTTP2</code> and then use
       the <code>http_X_ConnectionIsHTTP2</code> variable in
       the <code>if</code>-block above.
     </p>
     <p>
       Note that this configuration depends on the <code>if</code> construct,
       which <a href="https://www.nginx.com/resources/wiki/start/topics/depth/ifisevil/">is
       generally discouraged</a>.  Using <code>if</code> only to set variables in
       server blocks, however, is completely safe.
     </p>
    <p>
       For more details on script variables, including how to handle dollar
       signs, see <a href="system#nginx_script_variables">Script Variable
       Support</a>.
     </p>
   </div>
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	<html>
	<head>
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title>PageSpeed HTTPS Support</title>
	<link rel="stylesheet" href="doc.css">
	</head>
	<body>
	<!--#include virtual="_header.html" -->


	<div id=content>
	<h1>PageSpeed HTTPS Support</h1>
	<p class="note">
	As of version 1.10 HTTPS fetching (<code>FetchHttps</code>) is enabled by
	default, and PageSpeed no longer requires additional configuration to
	fetch and optimize resources over https. The alternatives described
	below, however, are more efficient in situations where they apply.
	</p>

	<p>
	PageSpeed supports sites that serve content through https. There are
	several mechanisms through which PageSpeed can be configured to fully
	optimize sites served under https:
	</p>
	<ul>
	<li>Use <code>MapOriginDomain</code> to
	<a href="https_support#map_the_origin">map the https domain to an http
	domain</a>.</li>
	<li>Use <code>LoadFromFile</code> to
	<a href="https_support#load_from_file">map a
	locally available directory to the https domain</a>.</li>
	<li>Use <code>FetchHttps</code> to <a href="https_support#https_fetch"
	>directly fetch HTTPS resources</a> (On by default since 1.10).</li>
	</ul>

	<p>
	The first two mechanisms can both be used on the same server, but they
	must be used for different domains, for example:
	</p>

	<dl>
	<dt>Apache:<dd><pre class="prettyprint"
	> ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
	ModPagespeedLoadFromFile "https://static.example.com" "/var/www/example/static/"</pre>
	</dd></dt>
	<dt>Nginx:<dd><pre class="prettyprint"
	> pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
	pagespeed LoadFromFile "https://static.example.com" "/var/www/example/static/";</pre>
	</dl>

	<p>
	Even without configuring any of these options, PageSpeed
	rewrites HTML documents requested via https. PageSpeed is able to
	serve these documents because the server passes the HTML document through
	all its output filters, including *_pagespeed. But by default,
	PageSpeed will only rewrite non-HTML resources which are served
	via http. Due to the complexity and security required to manage client
	SSL certificates, PageSpeed requires the server administrator to
	explicitly enable https fetching.
	</p>

	<p>
	The configuration options mentioned above are intended to help
	optimize sites with HTTPS resources. Fetching https resource URLs
	using http should be used only in installations where using http is
	safe, such as where the server running PageSpeed is a
	front-end to other back-end systems with private communications and
	mutual trust between them.
	</p>

	<h2 id="map_the_origin">Map the origin domain</h2>

	<p>
	Https resource URLs can be fetched by mapping them to a non-https origin
	domain as described in
	<a href="domains#mapping_origin">Mapping Origin Domains</a>:
	</p>
	<dl>
	<dt>Apache:<dd>
	<pre class="prettyprint">
	ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
	</pre>
	</dd></dt>
	<dt>Nginx:<dd>
	<pre class="prettyprint">
	pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
	</pre>
	</dd></dt>
	</dl>

	<p>
	This allows the server to accept https requests for
	<code>www.example.com</code> while fetching resources for it from the
	<code>localhost</code> http server, which could be the same Apache process or a
	different server process. All fetched resources will be optimized as usual. As
	many <code>MapOriginDomain</code> directives can be used as is required as long
	as https is only used on the second domain.
	</p>

	<h2 id="load_from_file">Load static files from disk</h2>

	<p>
	Https resource URLs can be served from static files using the
	<a href="domains#ModPagespeedLoadFromFile">LoadFromFile</a> directive:
	</p>

	<dl>
	<dt>Apache:<dd><pre class="prettyprint"
	>ModPagespeedLoadFromFile "https://www.example.com" "/var/www/example/static/";</pre>
	<dt>Nginx:<dd><pre class="prettyprint"
	>pagespeed LoadFromFile "https://www.example.com" "/var/www/example/static/";</pre>
	</dl>

	<h2 id="https_fetch">Fetch HTTPS resources directly</h2>
	<p>
	HTTPS fetching is built in and is enabled by default as of 1.10.33.0.
	To turn the feature off, set <code>FetchHttps</code> to
	<code>disable</code>:
	</p>

	<dl>
	<dt>Apache:<dd>
	<pre class="prettyprint">
	ModPagespeedFetchHttps enable
	</pre>
	</dd></dt>
	<dt>Nginx:<dd>
	<pre class="prettyprint">
	pagespeed FetchHttps enable;
	</pre>
	</dd></dt>
	</dl>
	<p>
	You may set multiple options, separated with a comma. For example, to
	test a configuration with a self-signed certificate you could do:
	</p>

	<dl>
	<dt>Apache:<dd>
	<pre class="prettyprint">
	ModPagespeedFetchHttps enable,allow_self_signed
	</pre>
	</dd></dt>
	<dt>Nginx:<dd>
	<pre class="prettyprint">
	pagespeed FetchHttps enable,allow_self_signed;
	</pre>
	</dd></dt>
	</dl>

	<p>
	The available options are
	<ul>
	<li><code>enable</code></li>
	<li><code>disable</code></li>
	<li><code>allow_self_signed</code></li>
	<li><code>allow_unknown_certificate_authority</code></li>
	<li><code>allow_certificate_not_yet_valid</code></li>
	</ul>
	</p>


	<h3 id="configuring_ssl_certificates">Configuring SSL Certificates</h3>

	<p>
	Acting as an HTTPS client, PageSpeed must be configured to point to a
	directory identifying trusted
	<a href="http://en.wikipedia.org/wiki/Certificate_authority"
	>Certificate Authorities</a> (not SSL keys for your domain). These settings will be automatically
	applied to configuration files for new binary installations on Debian,
	Ubuntu, and CentOS systems. Upgrades, source-installs, and other
	distributions may require manual configuration updates to identify the
	proper location.</p>

	<dl>
	<dt>Apache:<dd>
	<pre class="prettyprint">
	# Certificate Authorities directory, not your domain SSL keys
	ModPagespeedSslCertDirectory directory
	# Web Server's HTTPS client SSL key, not your domain SSL keys
	ModPagespeedSslCertFile file
	</pre>
	</dd></dt>
	<dt>Nginx:<dd>
	<pre class="prettyprint">
	pagespeed SslCertDirectory directory;
	pagespeed SslCertFile file;
	</pre>
	</dd></dt>
	</dl>

	<p>
	The default directory for Debian-based systems
	is <code>/etc/ssl/certs</code>, and there is no certificate file
	setting. On CentOS-based systems, the default directory
	is <code>/etc/pki/tls/certs</code> and default file
	is <code>/etc/pki/tls/cert.pem</code>.</p>

	<p>
	These directive cannot be used
	in <a href="configuration#htaccess"><code>.htaccess</code> files
	or <code><Directory></code></a> scopes.
	</p>

	<h2 id="rewrite_domains">Rewrite domains</h2>

	<p>
	Rewritten resources can have their https domain rewritten if required
	for the reasons described in <a href="domains#mapping_rewrite">Mapping Rewrite
	Domains</a>:
	</p>

	<dl>
	<dt>Apache:<dd><pre class="prettyprint"
	> ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
	ModPagespeedMapRewriteDomain "https://example.cdn.com" "https://www.example.com"</pre>
	</dd></dt>
	<dt>Nginx:<dd><pre class="prettyprint"
	> pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
	pagespeed MapRewriteDomain "https://example.cdn.com" "https://www.example.com";</pre>
	</dd></dt>
	</dl>

	<h2 id="shard_domains">Shard domains</h2>

	<p>
	Rewritten resources can have their https domain sharded if required
	for the reasons described in <a href="domains#shard">Sharding Domains</a>:
	</p>

	<dl>
	<dt>Apache:<dd><pre class="prettyprint"
	> ModPagespeedMapOriginDomain "http://localhost" "https://www.example.com"
	ModPagespeedShardDomain "https://www.example.com" \
	"https://example1.cdn.com,https://example2.cdn.com"</pre>
	</dd></dt>
	<dt>Nginx:<dd><pre class="prettyprint"
	> pagespeed MapOriginDomain "http://localhost" "https://www.example.com";
	pagespeed ShardDomain "https://www.example.com"
	"https://example1.cdn.com,https://example2.cdn.com";</pre>
	</dd></dt>
	</dl>

	<h2 id="RespectXForwardedProto">Respecting X-Forwarded-Proto</h2>
	<p>
	If you are running behind a load-balancer or other front-end that
	terminates the HTTPS connection and makes an HTTP subrequest to your
	server running PageSpeed, it will not know that the original URL was
	HTTPS and so it will rewrite subresources with <code>http://</code> URLs.
	For PageSpeed to operate correctly, it needs to know what
	the originally requested URL was. If your front-end sends
	<code>X-Forwarded-Proto</code> headers (as, for example,
	<a href="https://forums.aws.amazon.com/ann.jspa?annID=805">AWS Elastic
	Load Balancer does</a>) then you can tell PageSpeed to
	respect that header with:
	</p>
	<dl>
	<dt>Apache:<dd><pre class="prettyprint"
	> ModPagespeedRespectXForwardedProto on</pre>
	<dt>Nginx:<dd><pre class="prettyprint"
	> pagespeed RespectXForwardedProto on;</pre>
	</dl>
	<p>
	This will correctly rewrite your subresources with <code>https://</code>
	URLs and thus avoid mixed content warnings. Note, that you should only
	enable this option if you are behind a load-balancer that will set this
	header, otherwise your users will be able to set the protocol
	PageSpeed uses to interpret the request. Also, note that by default
	PageSpeed will loop back to the inbound ip/port for fetching resources
	on behalf of a html response using http(s). When X-Forwarded-Proto is in
	effect and the protocol is changed in front of the PageSpeed-enabled server,
	a mismatch may arise when performing loopback fetches, leading up to fetching
	failures. Explicitly authorizing the domain used to fetch resources will
	resolve this problem, because doing so allows the loopback fetching mechanism
	to be bypassed.
	</p>

	<p>
	This directive cannot be used
	in <a href="configuration#htaccess"><code>.htaccess</code> files
	or <code><Directory></code></a> scopes.
	</p>

	<h2 id="risks">Risks</h2>
	<p>
	As discussed above, using http to fetch https resources URLs should only be
	used when communication between the front-end and back-end servers is secure
	as otherwise the benefits of using https in the first place are lost. When
	fetching by HTTPS, <a
	href="https://boringssl.googlesource.com/boringssl/">BoringSSL</a>
	is used to authenticate the fetches. We bundle a copy of BoringSSL, which
	means that when security vulnerabilities are discovered that affect our usage
	we need to release updated versions of PageSpeed with the fixed BoringSSL
	library.
	</p>

	<h2 id="h2_configuration">HTTP/2-specific configuration</h2>
	<p>
	It's possible to tell PageSpeed to use a different configuration for
	clients using the HTTP/2 protocol than for clients using HTTP/1. You can
	configure this with the <code><If></code> construct in Apache and
	with script variables in Nginx.
	</p>
	<h3 id="h2_configuration_apache">Apache Version</h3>
	<p class="note">Note: Versions older than 1.12.34.1 provided
	a <code><ModPagespeedIf></code> construct. This is no longer supported, but
	configuration inside <code><ModPagespeedIf !spdy></code> blocks will be applied
	unconditionally for backwards compatibility.</p>

	<p>mod_http2 in Apache ≥ 2.4.19 provides an HTTP2 variable that can be used with the
	server's <code><If></code> construct to provide a different configuration for
	HTTP2 sessions. For example, one may want to disable some filters in such sessions, and only
	enable sharding in HTTP/1:
	<pre class="prettyprint">
	<If "%{HTTP2} == 'on'">
	ModPagespeedDisableFilters filter1,filter2
	</If>
	<Else>
	ModPagespeedShardDomain https://www.example.com https://example1.cdn.com,https://example2.cdn.com
	</Else></pre>

	<p>
	Note that this only covers requests terminated by mod_http2 on the Apache server itself.
	If an earlier proxy terminates HTTP/2, you may need to have it set a custom header,
	and test it using the <code>req</code> function.
	</p>

	<h3 id="h2_configuration_nginx">Nginx Version</h3>
	<p class="note"><strong>Note: New feature as of 1.10.33.0</strong></p>
	<pre class="prettyprint">
	http {
	pagespeed ProcessScriptVariables on;
	server {
	set $disable_filters "";
	set $domain_shards "shard1,shard2,shard3..."

	if ($http2) {
	set $disable_filters "filter1,filter2";
	set $domain_shards "";
	}
	pagespeed DisableFilters "$disable_filters";
	pagespeed ShardDomain domain_to_shard "$domain_shards";
	}
	}</pre>
	<p>
	The <code>$http2</code> variable is defined by
	the <a href="http://nginx.org/en/docs/http/ngx_http_v2_module.html"
	><code>ngx_http_v2_module</a></code>, and will be non-empty on any
	connection over HTTP/2.
	</p>
	<p>
	If the connection is terminated on another server
	the <code>$http2</code> variable won't be available. In that case, you
	can have the other server add a header for HTTP/2 connections
	like <code>X-ConnectionIsHTTP2</code> and then use
	the <code>http_X_ConnectionIsHTTP2</code> variable in
	the <code>if</code>-block above.
	</p>
	<p>
	Note that this configuration depends on the <code>if</code> construct,
	which <a href="https://www.nginx.com/resources/wiki/start/topics/depth/ifisevil/">is
	generally discouraged</a>. Using <code>if</code> only to set variables in
	server blocks, however, is completely safe.
	</p>
	<p>
	For more details on script variables, including how to handle dollar
	signs, see <a href="system#nginx_script_variables">Script Variable
	Support</a>.
	</p>
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