Serving the right language via content negotiation
3 min. read
**The problem Statement**: I want the server to deliver the right document (variant) based on the browser's language preferences. Browsers send an Accept-Language header which lists their preferred language(s).
## Apache
Before we configure our language negotiation parameters we need to set up things on the server. You can set this on the default `httpd.conf` configuration file (meaning that it'll work in all virtual hosts) or you can set in in each virtual host configuration (meaning it'll only work for that virtual host)
The two items are:
- `LanguagePriority` allows you the language precedence during content negotiation. If more than one version of a file is available
- `ForceLanguagePriority` allows you to serve a result page rather than MULTIPLE CHOICES (Prefer) in case of a tie or NOT ACCEPTABLE (Fallback) in case no accepted languages matched the available variants.
```apacheconf
LanguagePriority en-US en ca cs de el es pt pt-BR zh-CN zh-TW
ForceLanguagePriority Prefer Fallback
```
### MultiViews
MultiViews works as follows: if you request a resource named foo, and foo does not exist in the directory, Apache will search for all files named `foo.*`, like `foo.html`, `foo.html.de`, `foo.html.en`, `foo.de.html`, `foo.en.html`, `foo.en.html.gz`, `foo.gz.en.html`, `foo.html.gz.en`, `foo.html.en.gz`, and so on.
If we have this and the client's browser is configured with German as the primary language then the server will send `index.html.de` as the first option.
```bash
root@server1:~# ls -la /var/www/
total 20
drwxr-xr-x 2 root root 4096 Jul 20 00:13 .
drwxr-xr-x 14 root root 4096 Feb 14 18:43 ..
-rw-r--r-- 1 root root 196 Jul 20 00:06 index.html.de
-rw-r--r-- 1 root root 186 Jul 20 00:03 index.html.en
-rw-r--r-- 1 root root 207 Jul 20 00:09 index.html.fr
root@server1:~#
```
MultiViews is a per-directory setting, i.e., it has to be set with an Options directive in a ``, ``, or `` section in the Apache configuration. It has to be set explicitly with `Options MultiViews`. Using `Options All` does not set it.
The documentation for [options](https://httpd.apache.org/docs/2.4/mod/core.html#options) lists valid values you can use in the directive.
```apacheconf
Options Indexes FollowSymLinks MultiViews
DirectoryIndex index.html
AllowOverride None
Order allow,deny
allow from all
```
That's basically all we need for content negotiation. Using Language Priority, Force Language Priority and multiviews allow Apache to handle multiple versions of a page without us having to do anything on the client other than writing the different versions of the page.
## Nginx
The code is taken from this [serverfault](https://serverfault.com/questions/815168/serve-different-files-depending-on-the-browser-language) answer.
If the browser sends headers like this one: `accept-language: en,en-US;q=0.8,ja;q=0.6` we can configure the server to handle content negotiation with the following block.
The configuration does the following:
1. Sets the variable `$first_language` to the value of the accept-language header
2. Matches the string to the fir comma. This can be just the top level language code (`en`), the language and country code (`en-US`) or the language plus qualifier (`en-US;q=0.8`)
3. Set the default suffix to a language. In this case, English (en)
4. If the first language is Japanese (`ja`) then set the language suffix to Japanese
This will make the server render the page with the given language suffix.
```nginx
set $first_language $http_accept_language; #1
if ($http_accept_language ~* '^(.+?),') {
set $first_language $1;
}
set $language_suffix 'en';
if ($first_language ~* 'ja') {
set $language_suffix 'ja';
}
```
One shortcoming of this approach is that we need to have a list of our supported languages in hand as we prepare this configuration and every time we add a language we have to add if statements to the later block.
The [nginx\_accept\_language\_module](https://www.nginx.com/resources/wiki/modules/accept_language/) module parses the `Accept-Language` field in HTTP headers and chooses the most suitable locale for the user from the list of locales supported at your website.
