System requirements

To run Contao successfully, the web server must meet these system requirements. Contao was originally developed for the familiar LAMP stack, but runs on any web server that provides a current version of PHP and MySQL.

Software Recommendations

The minimum requirements depend on whether you are installing the latest or the Long Term Support version. All maintained versions of Contao are compatible with the latest PHP and MySQL versions. Therefore, we recommend to always use them.

• PHP: Version 7.4+ (latest patch version)
• MySQL: Version 8.0+ or equivalent MariaDB server

PHP Extensions

$ vendor/bin/contao-console debug:container contao.image.imagine

All required extensions are enabled by default in current PHP versions. However, some hosting providers explicitly disable them. The requirements are automatically checked during installation via the Contao Manager or Composer.

PHP configuration (php.ini)

These are the recommended settings for the ideal operation of Contao. A different configuration does not mean that Contao does not work, but may cause unexpected behavior or performance degradation/slow reactions.

MySQL Configuration

• MySQL storage engine InnoDB (default since MySQL 5.7)
• MySQL option innodb_large_prefix = 1 (enabled by default since MySQL 5.7.7)
• MySQL option innodb_file_format = Barracuda (not necessary any more since MySQL 8.0)
• MySQL option innodb_file_per_table = 1 (enabled by default since MySQL 5.6.7)
• MySQL character set utf8mb4

Minimum PHP Requirements

Contao 5.0 and later

• PHP Version 8.1.0 or higher is required.

Contao 4.13 (LTS)

• PHP Version 7.4.0 or higher is required.

Contao 4.9 (LTS)

• PHP Version 7.2.0 or higher is required.
• Images can be processed with the PHP extensions GD (ext-gd), Imagick (ext-imagick) or Gmagick (ext-gmagick). Contao automatically detects and uses the best available extension.

Contao 4.4 (LTS)

• PHP Version 5.6.0 or higher is required.
• The GD extension (ext-gd) is required for image processing.

Switching the PHP version

In case you want to switch the PHP version of an already running PHP instance, you should always run a full composer update after switching. This is especially important when switching between major versions, e.g. from PHP 7.x to 8.x - or vice versa. This ensures compatibility of your installed packages with the respective PHP version, since each package (including Contao itself, installed Contao extensions and other third-party packages) can require specific PHP versions and PHP extensions that it needs and is known to be compatible with.

In case you are using the Contao Manager, you can run the composer update process in the maintenance section under Composer Dependencies:

MySQL minimum requirements

Although Contao uses the Doctrine DBAL database abstraction layer, no database server types other than MySQL (or a compatible fork like MariaDB) are currently supported.

Contao has been successfully tested on MySQL servers version 5.7 / 8.0 (and equivalent MariaDB versions) with InnoDB table format. The use of utf8 instead of the utf8mb4 character set results in a worse UTF8 support (e.g. no emojis).

If the above recommended options cannot be enabled on your server, please configure a different character set in your config/config.yaml file:

doctrine:
    dbal:
        connections:
            default:
                default_table_options:
                    charset: utf8
                    collate: utf8_unicode_ci
                    collation: utf8_unicode_ci

It is further recommended to run MySQL in “strict mode” to prevent corrupt or truncated data and to guarantee data integrity.

To enable it, add the following to your my.cnf or my.ini file or make sure that the setting is adjusted accordingly:

[mysqld]
…
sql_mode="TRADITIONAL"
…

If the setting cannot be enabled on your server, please configure the connection options in your config/config.yaml file:

doctrine:
    dbal:
        connections:
            default:
                options:
                    # Depending on the DB driver, the option key is either 1002 (pdo_mysql) or 3 (mysqli)
                    1002: "SET SESSION sql_mode=(SELECT CONCAT(@@sql_mode, ',TRADITIONAL'))"

Web server

• Modern hosting environments of today allow customers to access their account via an SSH terminal. This is not only a more secure connection than traditional unencrypted FTP, but also allows efficient debugging and the development of the application.

• It is recommended to use PHP-FPM or a similar FastCGI setup for the PHP stack. Contao can perform background tasks (such as indexing the page content) without the browser waiting for the response by using fastcgi_finish_request().

Hosting configuration

In Contao, all publicly accessible files are located in the web/ subfolder of the installation. Set the document root of the installation via the admin panel of the hosting provider to this subfolder and set up a database on this occasion.

Example: example.com points to the directory /www/example/web

(since 4.12 Following the Symfony standard, the public subfolder of /web has been renamed to /public. If there is a /web directory in your installation, Contao will automatically use it instead of /public).

since 4.13 If your installation is still using the folder /web as its public directory, explicitly set it in the composer.json of the project in order to be prepared for future versions of contao:

{
  "extra": {
    "public-dir": "web"
  }
}

see also: https://symfony.com/doc/current/configuration/override_dir_structure.html#override-the-public-directory

Web server configuration

Within the configuration of your web server you will need to make sure that all requests are processed by the index.php in the public directory, typically via URL rewriting. How to achieve this depends on the type of web server you are running. The most common ones are Apache and NGINX:

<VirtualHost *:80>
    ServerName domain.tld
    ServerAlias www.domain.tld
    DocumentRoot /var/www/project/public

    <Directory /var/www/project/public>
        AllowOverride All
        Require all granted
        Options SymLinksIfOwnerMatch
    </Directory>
</VirtualHost>

server {
    server_name domain.tld www.domain.tld;
    root /var/www/project/public;

    location / {
        try_files $uri /index.php$is_args$args;
    }

    # main entry point
    location ~ ^/index\.php(/|$) {
        # the exact FastCGI configuration depends on your environment
        fastcgi_pass unix:/var/run/php/php8.1-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi.conf;
        internal;
    }

    # also allow preview.php and contao-manager.phar.php to be processed
    location ~ ^/(preview|contao-manager\.phar)\.php(/|$) {
        # the exact FastCGI configuration depends on your environment
        fastcgi_pass unix:/var/run/php/php8.1-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi.conf;
    }
}

You can also find more information about the configuration of your web server in the Symfony documentation.

Provider-specific settings

There are a few major Internet service providers that offer special settings for running Contao. Fortunately, they are only the exception to the rule. The provider-specific settings can be found in the German Contao forum. You can get optimal hosting packages for Contao from the Contao partners in the service category “Web hosting”.