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HTML5 Boilerplate homepage | Documentation table of contents

.htaccess

In Apache HTTP server, .htaccess (hypertext access) is the configuration file that allows for web server configuration. HTML5 Boilerplate includes a number of best practice server rules for making web pages fast and secure, these rules can be applied in the .htaccess file.

First, you'll want to have these modules enabled for optimum performance:

  • mod_setenvif.c (setenvif_module)
  • mod_headers.c (headers_module)
  • mod_deflate.c (deflate_module)
  • mod_filter.c (filter_module)
  • mod_expires.c (expires_module)
  • mod_rewrite.c (rewrite_module)

On Windows

You've got a couple of options that depend on how you installed Apache.

  1. WampServer. This is by far the simplest option. If you have installed WampServer just click on the icon in the task bar, hover over the Apache section in the menu that comes up and then hover over the modules section. You will be presented with a list of modules. Simply click on a module name to enable it (or disable it if it is already enabled). A check mark next to a module indicates that it is enabled. WampServer will automatically restart the Apache service after you enable a module.

  2. Manually editing httpd.conf. This assumes that you have manually installed Apache. You will need to locate the httpd.conf file which is normally in the conf folder in the folder where you installed Apache (for example C:\apache\conf\httpd.conf). Open up this file in a text editor. Near the top (after a bunch of comments) you will see a long list of modules. Check to make sure that the modules listed above are not commented out. If they are, go ahead and uncomment them and restart Apache.

That's it, you're done!

On Linux

These instructions should work on any distribution where apt-get has been used to install Apache.

  1. Open up a terminal and type the following command. Enter your password when prompted.

    sudo a2enmod setenvif headers deflate filter expires rewrite include

  2. Restart apache by using the following command so the new configuration takes effect.

    sudo /etc/init.d/apache2 restart

That's it, you're done!

On Mac

  1. MAMP PRO. On the main screen, click the Apache tab and ensure that all the required modules listed above are 'checked', indicating they are enabled.

  2. MAMP. Locate the httpd.conf file, which is typically found in /Applications/MAMP/conf/apache/httpd.conf. Open the file in a text editor and uncomment all of the required modules listed above. Once you have done so, reset MAMP.

  3. XAMPP. Follow the same steps as for MAMP, but look for httpd.conf in /Applications/XAMPP/etc/httpd.conf.

Security

Do not turn off your ServerSignature (i.e., the Server: HTTP header). Serious attackers can use other kinds of fingerprinting methods to figure out the actual server and components running behind a port. Instead, as a site owner, you should keep track of what's listening on ports on hosts that you control. Run a periodic scanner to make sure nothing suspicious is running on a host you control, and use the ServerSignature to determine if this is the web server and version that you expect.

Performance

Configure ETags

FileETag None

Entity tags (ETags) is a mechanism that web servers and browsers use to determine whether the component in the browser's cache matches the one on the origin server. (An "entity" is another word for "component": images, scripts, stylesheets, etc.) ETags were added to provide a mechanism for validating entities that is more flexible than the last-modified date. An ETag is a string that uniquely identifies a specific version of a component. The only format constraints are that the string be quoted. The origin server specifies the component's ETag using the ETag response header.

HTTP/1.1 200 OK
Last-Modified: Tue, 12 Dec 2006 03:03:59 GMT
ETag: "10c24bc-4ab-457e1c1f"
Content-Length: 12195

Later, if the browser has to validate a component, it uses the If-None-Match header to pass the ETag back to the origin server. If the ETags match, a 304 status code is returned reducing the response by 12195 bytes for this example.

GET /i/yahoo.gif HTTP/1.1
Host: us.yimg.com
If-Modified-Since: Tue, 12 Dec 2006 03:03:59 GMT
If-None-Match: "10c24bc-4ab-457e1c1f"
HTTP/1.1 304 Not Modified

The problem with ETags is that they typically are constructed using attributes that make them unique to a specific server hosting a site. ETags won't match when a browser gets the original component from one server and later tries to validate that component on a different server, a situation that is all too common on web sites that use a cluster of servers to handle requests. By default, both Apache and IIS embed data in the ETag that dramatically reduces the odds of the validity test succeeding on web sites with multiple servers.

The ETag format for Apache 1.3 and 2.x is inode-size-timestamp. Although a given file may reside in the same directory across multiple servers, and have the same file size, permissions, timestamp, etc., its inode is different from one server to the next.

IIS 5.0 and 6.0 have a similar issue with ETags. The format for ETags on IIS is Filetimestamp:ChangeNumber. A ChangeNumber is a counter used to track configuration changes to IIS. It's unlikely that the ChangeNumber is the same across all IIS servers behind a web site.

The end result is ETags generated by Apache and IIS for the exact same component won't match from one server to another. If the ETags don't match, the user doesn't receive the small, fast 304 response that ETags were designed for; instead, they'll get a normal 200 response along with all the data for the component. If you host your web site on just one server, this isn't a problem. But if you have multiple servers hosting your web site, and you're using Apache or IIS with the default ETag configuration, your users are getting slower pages, your servers have a higher load, you're consuming greater bandwidth, and proxies aren't caching your content efficiently. Even if your components have a far future Expires header, a conditional GET request is still made whenever the user hits Reload or Refresh.

If you're not taking advantage of the flexible validation model that ETags provide, it's better to just remove the ETag altogether. The Last-Modified header validates based on the component's timestamp. And removing the ETag reduces the size of the HTTP headers in both the response and subsequent requests. This Microsoft Support article describes how to remove ETags. In Apache, this is done by simply adding the above line to your Apache configuration file.

Gzip Components

Compression reduces response times by reducing the size of the HTTP response.

Starting with HTTP/1.1, web clients indicate support for compression with the Accept-Encoding header in the HTTP request.

Accept-Encoding: gzip, deflate

If the web server sees this header in the request, it may compress the response using one of the methods listed by the client. The web server notifies the web client of this via the Content-Encoding header in the response.

Content-Encoding: gzip

Gzip is the most popular and effective compression method at this time. It was developed by the GNU project and standardized by RFC 1952. The only other compression format you're likely to see is deflate, but it's less effective and less popular.

Gzipping generally reduces the response size by about 70%. Approximately 90% of today's Internet traffic travels through browsers that claim to support gzip. If you use Apache, the module configuring gzip depends on your version: Apache 1.3 uses mod_gzip while Apache 2.x uses mod_deflate.

There are known issues with browsers and proxies that may cause a mismatch in what the browser expects and what it receives with regard to compressed content. Fortunately, these edge cases are dwindling as the use of older browsers drops off. The Apache modules help out by adding appropriate Vary response headers automatically.

Servers choose what to gzip based on file type, but are typically too limited in what they decide to compress. Most web sites gzip their HTML documents. It's also worthwhile to gzip your scripts and stylesheets, but many web sites miss this opportunity. In fact, it's worthwhile to compress any text response including XML and JSON. Image and PDF files should not be gzipped because they are already compressed. Trying to gzip them not only wastes CPU but can potentially increase file sizes.

Gzipping as many appropriate file types as possible is an easy way to reduce page weight and accelerate the user experience.

Cache busting

A first-time visitor to your page may have to make several HTTP requests, but by using the Expires header you make those components cacheable. This avoids unnecessary HTTP requests on subsequent page views. Expires headers are most often used with images, but they should be used on all components including scripts, stylesheets, etc.

Traditionally, if you use a far future Expires header you have to change the component's filename whenever the component changes.

The H5BP .htaccess has built-in filename cache busting. To use it, uncomment the relevant lines in the .htaccess file.

Doing so will route all requests for /path/filename.20120101.ext to /path/filename.ext. To use this, just add a time-stamp number (or your own numbered versioning system) into your resource filenames in your HTML source whenever you update those resources.

Example:

<script src="/js/myscript.20120305.js"></script>
<script src="/js/jqueryplugin.45.js"></script>
<link rel="stylesheet" href="css/somestyle.49559939932.css">
<link rel="stylesheet" href="css/anotherstyle.2.css">

N.B. You do not have to rename the resource on the filesystem. All you have to do is add the timestamp number to the filename in your HTML source. The .htaccess directive will serve up the proper file.

Traditional cache busting involved adding a query string to the end of your JavaScript or CSS filename whenever you updated it.

<script src="/js/all.js?v=12"></script>

However, as Steve Souders explains in Revving Filenames: don’t use querystring, the query string approach is not always reliable for clients behind a Squid Proxy Server.

Trailing slash redirects

Trailing slash redirects can be done by adding one of the options below in .htaccess.

Option 1

Rewrite domain.com/foo -> domain.com/foo/.

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/|#(.*))$
RewriteRule ^(.*)$ $1/ [R=301,L]

Option 2

Rewrite domain.com/foo/ -> domain.com/foo

RewriteRule ^(.*)/$ $1 [R=301,L]

Here are some tips to show you how to integrate the rewrite rules with different CMS tools. There are four areas you need to look out for:

1. Keep a backup

If you use trailing slash redirects on an existing site, always keep a backup of your .htaccess and test thoroughly on your staging server before using it on a production server.

2. Don't replace existing rules, merge

For example, if you use CodeIgniter you may have existing URL rewrite rules like:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1

Merge the above with H5BP rules below:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/|#(.*))$
RewriteRule ^(.*)$ $1/ [R=301,L]

3. Be careful of the order

Make sure you test thoroughly in your staging environment. For the above example, the order is add trailing slash first, and add your existing rule after:

# this adds trailing slash
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/|#(.*))$
RewriteRule ^(.*)$ $1/ [R=301,L]

# this gets rid of index.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1

4. Double-check RewriteBase path is correct

Make sure your RewriteBase path points to the correct location and sits above any rewrite rules. This usually happens to those have WordPress and ran the auto install. For instance, if you have a site at example.com/blog, your RewriteBase may look like:

RewriteBase /blog/

If you already have a working RewriteBase, keep that and don't remove it.