Version 4 supported
This version of Silverstripe CMS is still supported though will not receive any additional features. Go to documentation for the most recent stable version.


Silverstripe CMS needs to be installed on a web server. Content authors and website administrators use their web browser to access a web-based GUI to do their day-to-day work. Website designers and developers require access to the files on the server to update templates, website logic, and perform upgrades or maintenance.


  • PHP >=7.4, <=8.1
  • PHP extensions: ctype, dom, fileinfo, hash, intl, mbstring, session, simplexml, tokenizer, xml
  • PHP configuration: memory_limit with at least 48M
  • PHP extension for image manipulation: Either gd or imagick
  • PHP extension for a database connector (e.g. pdo or mysqli)

Use phpinfo() to inspect your configuration.

Silverstripe CMS tracks the official PHP release support timeline. When a PHP version reaches end-of-life, Silverstripe CMS drops support for it in the next minor release.


Default MySQL collation

In Silverstripe CMS Recipe 4.7 and later, new projects default to the utf8mb4_unicode_ci collation when running against MySQL, which offers better support for multi-byte characters such as emoji. However, this may cause issues related to Varchar fields exceeding the maximum indexable size:

  • MySQL 5.5 and lower cannot support indexes larger than 768 bytes (192 characters)
  • MySQL 5.6 supports larger indexes (3072 bytes) if the innodb_large_prefix setting is enabled (but not by default)
  • MySQL 5.7 and newer have innodb_large_prefix enabled by default
  • MariaDB ~10.1 matches MySQL 5.6's behaviour, >10.2 matches 5.7's.

You can rectify this issue by upgrading MySQL, enabling the innodb_large_prefix setting if available, or reducing the size of affected fields. If none of these solutions are currently suitable, you can remove the new collation configuration from app/_config/mysite.yml to default back to the previous default collation.

Existing projects that upgrade to Recipe 4.7.0 will unintentionally adopt this configuration change. Recipe 4.7.1 and later are unaffected. See the release notes for more information.

Connection mode (sql_mode) when using MySQL server >=5.7.5

In MySQL versions >=5.7.5, the ANSI sql_mode setting behaves differently and includes the ONLY_FULL_GROUP_BY setting. It is generally recommended to leave this setting as-is because it results in deterministic SQL. However, for some advanced cases, the sql_mode can be configured on the database connection via the configuration API ( see MySQLDatabase::$sql_mode for more details.) This setting is only available in Silverstripe CMS 4.7 and later.

MySQL/MariaDB int width in schema

MySQL 8.0.17 stopped reporting the width attribute for integers while MariaDB did not change its behaviour. This results in constant rebuilding of the schema when MySQLSchemaManager expects a field to look like e.g. INT(8) and MySQL server reports it simply as INT. MySQLSchemaManager has been updated to detect the MySQL server implementation and act accordingly. In cases when auto-detection fails, you can force the desired behaviour like this:

    schema_use_int_width: true # or false when INT widths should be ignored

Webserver configuration


Silverstripe CMS needs to handle a variety of HTTP requests, and relies on the hosting environment to be configured securely to enforce restrictions. There are secure defaults in place for Apache, but you should be aware of the configuration regardless of your webserver setup.

Public webroot

The webroot of your webserver should be configured to the public/ subfolder. Projects created prior to Silverstripe CMS 4.1 might be using the main project folder as the webroot. In this case, you are responsible for ensuring access to system files such as configuration in *.yml is protected from public access. We strongly recommend switching to more secure hosting via the public/. See 4.1.0 upgrading guide.

Filesystem permissions

During runtime, Silverstripe CMS needs read access for the webserver user to your base path (including your webroot). It also needs write access for the webserver user to the following locations:

  • public/assets/: Used by the CMS and other logic to store uploads
  • TEMP_PATH: Temporary file storage used for the default filesystem-based cache adapters in Manifests, Object Caching and Partial Template Caching. See Environment Management.
  • .graphql-generated: silverstripe/graphql version 4 introduces this directory. This is where your schema is stored once it has been built. Best practice is to create it ahead of time, but if the directory doesn't exist and your project root is writable, the GraphQL module will create it for you.
  • public/_graphql: silverstripe/graphql version 4 introduces this directory. It's used for schema introspection. You should treat this folder the same way you treat the .graphql-generated folder.

If you are still using silverstripe/graphql 3.x, you do not need the .graphql-generated or public/_graphql directories.

If you aren't explicitly packaging your Silverstripe CMS project during your deployment process, additional write access may be required to generate supporting files on the fly. This is not recommended, because it can lead to extended execution times as well as cause inconsistencies between multiple server environments when manifest and cache storage isn't shared between servers.

Note that permissions may be required for other directories for specific functionality - for example if you use the i18nTextCollector you will need to provide write access to the relevant i18n lang directories.


Silverstripe CMS allows CMS authors to upload files into the public/assets/ folder, which should be served by your webserver. No PHP execution should be allowed in this folder. This is configured for Apache by default via public/assets/.htaccess. The file is generated dynamically during the dev/build stage.

Additionally, access is whitelisted by file extension through a dynamically generated whitelist based on the File.allowed_extensions setting (see File Security). This whitelist uses the same defaults configured through file upload through Silverstripe CMS, so is considered a second line of defence.

Secure assets

Files can be kept in draft stage, and access restricted to certain user groups. These files are stored in a special .protected/ folder (defaulting to public/assets/.protected/). Requests to files in this folder should be denied by your webserver.

Requests to files in the .protected/ folder are routed to PHP by default when using Apache, through public/assets/.htaccess. If you are using another webserver, please follow our guides to ensure a secure setup. See Developer Guides: File Security for details.

For additional security, we recommend moving the .protected/ folder out of public/assets/. This removes the possibility of a misconfigured webserver accidentally exposing these files under URL paths, and forces read access via PHP.

This can be configured via .env variable, relative to the index.php location.


The resulting folder structure will look as follows:


Don't forget to include this additional folder in any syncing and backup processes!

Building, packaging and deployment

It is common to build a Silverstripe CMS application into a package on one environment (e.g. a CI server), and then deploy the package to a (separate) webserver environment(s). This approach relies on all auto-generated files required by Silverstripe CMS to be included in the package, or generated on the fly on each webserver environment.

The easiest way to ensure this is to commit auto generated files to source control. If those changes are considered too noisy, here's some pointers for auto-generated files to trigger and include in a deployment package:

Web worker concurrency

It's generally a good idea to run multiple workers to serve multiple HTTP requests to Silverstripe CMS concurrently. The exact number depends on your website needs. The CMS attempts to request multiple views concurrently. It also routes protected and draft files through Silverstripe CMS. This can increase your concurrency requirements, e.g. when authors batch upload and view dozens of draft files in the CMS.

When allowing upload of large files through the CMS (through PHP settings), these files might be used as protected and draft files. Files in this state get served by Silverstripe CMS rather than your webserver. Since the framework uses PHP streams, this allows serving of files larger than your PHP memory limit. Please be aware that streaming operations don't count towards PHP's max_execution_time, which can risk exhaustion of web worker pools for long-running downloads.

URL rewriting

Silverstripe CMS expects URL paths to be rewritten to public/index.php. For Apache, this is preconfigured through .htaccess files, and expects using the mod_rewrite module. By default, these files are located in public/.htaccess and public/assets/.htaccess.

HTTP headers

Silverstripe CMS can add HTTP headers to responses it handles directly. These headers are often sensitive, for example preventing HTTP caching for responses displaying data based on user sessions, or when serving protected assets. You need to ensure those headers are kept in place in your webserver. For example, Apache allows this through Header setifempty (see docs). See Developer Guide: Performance and Developer Guides: File Security for more details.

Silverstripe CMS relies on the Host header to construct URLs such as "reset password" links, so you'll need to ensure that the systems hosting it only allow valid values for this header. See Developer Guide: Security - Request hostname forgery .

CDNs and other reverse proxies

If your Silverstripe CMS site is hosted behind multiple HTTP layers, you're in charge of controlling which forwarded headers are considered valid, and which IPs can set them. See Developer Guide: Security - Request hostname forgery .


Silverstripe CMS is a modular system, with modules installed and updated via the composer PHP dependency manager. These are usually stored in vendor/, outside of the public/ webroot. Since many modules rely on serving frontend assets such as CSS files or images, these are mapped over to the public/_resources/ folder automatically. If the filesystem supports it, this is achieved through symlinks. Depending on your hosting and deployment mechanisms, you may need to configure the plugin to copy files instead. See silverstripe/vendor-plugin for details.


Silverstripe CMS relies on various caches to achieve performant responses. By default, those caches are stored in a temporary filesystem folder, and are not shared between multiple server instances. Alternative cache backends such as Redis can be configured.

While cache objects can expire, when using filesystem caching the files are not actively pruned. For long-lived server instances, this can become a capacity issue over time - see workaround.

Error pages

The default installation includes silverstripe/errorpage, which generates static error pages that bypass PHP execution when those pages are published in the CMS. Once published, the static files are located in public/assets/error-404.html and public/assets/error-500.html. The default public/.htaccess file is configured to have Apache serve those pages based on their HTTP status code.

Other webservers (Nginx, IIS, Lighttpd)

Serving through webservers other than Apache requires more manual configuration, since the defaults configured through .htaccess don't apply. Please apply the considerations above to your webserver to ensure a secure hosting environment. In particular, configure protected assets correctly to avoid exposing draft or protected files uploaded through the CMS.

There are various community supported installation instructions for different environments. Nginx is a popular choice, see Nginx webserver configuration.

Silverstripe CMS is known to work with Microsoft IIS, and generates web.config files by default ( see Microsoft IIS and SQL Server configuration) .

Additionally, there are community supported guides for installing Silverstripe CMS on various environments:


Silverstripe CMS uses SwiftMailer to send email messages. New installations setup with silverstripe/installer are configured to use a sendmail found in /usr/sbin/sendmail or another location specified via configuration. Alternatively email can be configured to use SMTP or other mail transports instead of sendmail.

You must ensure emails are being sent from your production environment. You can do this by testing that the Lost password form available at /Security/lostpassword sends an email to your inbox, or with the following code snippet that can be run via a SilverStripe\Dev\BuildTask:

use SilverStripe\Control\Email\Email;

$email = Email::create('', '', 'My test subject', 'My email body text');

Using the code snippet above also tests that the ability to set the "from" address is working correctly.

See the email section for further details, including how to set the administrator "from" email address, change the sendmail binary location and how to use SMTP or other mail transports instead of sendmail.

PHP requirements for older Silverstripe CMS releases

Silverstripe CMS's PHP support has changed over time and if you are looking to upgrade PHP on your Silverstripe CMS site, this table may be of use:

Silverstripe CMS VersionPHP VersionMore information
4.11 +7.4 - 8.1changelog
4.107.3 - 8.0changelog
4.5 - 4.97.1 - 7.4blog post
4.0 - 4.45.6 - 7.4

From Silverstripe CMS 5 onwards, the Silverstripe CMS major release policy guides which PHP versions are supported by which Silverstripe CMS release.

CMS browser requirements

Silverstripe CMS supports the following web browsers:

  • Google Chrome
  • Microsoft Edge
  • Mozilla Firefox

We aim to provide satisfactory experiences in Apple Safari. Silverstripe CMS works well across Windows, Linux, and Mac operating systems.

End user requirements

Silverstripe CMS is designed to make excellent, standards-compliant websites that are compatible with a wide range of industry standard browsers and operating systems. A competent developer is able to produce websites that meet W3C guidelines for HTML, CSS, JavaScript, and accessibility, in addition to meeting specific guide lines, such as e-government requirements.