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.

How to extend the CMS interface


The CMS interface works just like any other part of your website: It consists of PHP controllers, templates, CSS stylesheets and JavaScript. Because it uses the same base elements, it is relatively easy to extend.

As an example, we're going to add a permanent "bookmarks" link list to popular pages into the main CMS menu. A page can be bookmarked by a CMS author through a simple checkbox.

For a deeper introduction to the inner workings of the CMS, please refer to our guide on CMS Architecture.

Overload a CMS template

If you place a template with an identical name into your application template directory (usually app/templates/), it'll take priority over the built-in one.

CMS templates are inherited based on their controllers, similar to subclasses of the common Page object (a new PHP class MyPage will look for a template). We can use this to create a different base template with (which corresponds to the LeftAndMain PHP controller class).

Copy the template markup of the base implementation at templates/SilverStripe/Admin/Includes/ from the silverstripe/admin module into app/templates/SilverStripe/Admin/Includes/ It will automatically be picked up by the CMS logic. Add a new section into the <ul class="cms-menu__list">

<ul class="cms-menu-list">
    <!-- ... -->
    <li class="bookmarked-link first">
        <a href="{$AdminURL}pages/edit/show/1">Edit "My popular page"</a>
    <li class="bookmarked-link last">
        <a href="{$AdminURL}pages/edit/show/99">Edit "My other page"</a>

Refresh the CMS interface with admin/?flush=all, and you should see those hardcoded links underneath the left-hand menu. We'll make these dynamic further down.

Include custom CSS in the CMS

In order to show the links a bit separated from the other menu entries, we'll add some CSS, and get it to load with the CMS interface. Paste the following content into a new file called app/css/BookmarkedPages.css:

.bookmarked-link.first {margin-top: 1em;}

Load the new CSS file into the CMS, by setting the LeftAndMain.extra_requirements_css configuration value.

    - app/css/BookmarkedPages.css

In order to let the frontend have the access to our css files, we need to expose them in the composer.json:

    "extra": {
        "expose": [

Then run composer vendor-expose. This command will publish all the css files under the app/css folder to their public-facing paths.

Note: don't forget to flush.

Create a "bookmark" flag on pages

Now we'll define which pages are actually bookmarked, a flag that is stored in the database. For this we need to decorate the page record with a DataExtension. Create a new file called app/src/BookmarkedPageExtension.php and insert the following code.

namespace App\Extension;

use SilverStripe\Forms\CheckboxField;
use SilverStripe\Forms\FieldList;
use SilverStripe\ORM\DataExtension;

class BookmarkedPageExtension extends DataExtension
    private static $db = [
        'IsBookmarked' => 'Boolean',

    public function updateCMSFields(FieldList $fields)
            new CheckboxField('IsBookmarked', 'Show in CMS bookmarks?')

Enable the extension in your configuration file

    - App\Extension\BookmarkedPageExtension

In order to add the field to the database, run a dev/build/?flush=all. Refresh the CMS, open a page for editing and you should see the new checkbox.

Retrieve the list of bookmarks from the database

One piece in the puzzle is still missing: How do we get the list of bookmarked pages from the database into the template we've already created (with hardcoded links)? Again, we extend a core class: The main CMS controller called LeftAndMain.

Add the following code to a new file app/src/BookmarkedLeftAndMainExtension.php;

namespace App\Extension;

use SilverStripe\Admin\LeftAndMainExtension;

class BookmarkedPagesLeftAndMainExtension extends LeftAndMainExtension
    public function getBookmarkedPages()
        return Page::get()->filter('IsBookmarked', 1);

Enable the extension in your configuration file

    - App\Extension\BookmarkedPagesLeftAndMainExtension

As the last step, replace the hardcoded links with our list from the database. Find the <ul> you created earlier in app/templates/SilverStripe/Admin/Includes/ and replace it with the following:

<ul class="cms-menu__list">
    <!-- ... -->
    <% loop $BookmarkedPages %>
    <li class="bookmarked-link $FirstLast">
        <li><a href="{$AdminURL}pages/edit/show/$ID">Edit "$Title"</a></li>
    <% end_loop %>

Extending the CMS actions

CMS actions follow a principle similar to the CMS fields: they are built in the backend with the help of FormFields and FormActions, and the frontend is responsible for applying a consistent styling.

The following conventions apply:

  • New actions can be added by redefining getCMSActions, or adding an extension with updateCMSActions.
  • It is required the actions are contained in a FieldList (getCMSActions returns this already).
  • Standalone buttons are created by adding a top-level FormAction (no such button is added by default).
  • Button groups are created by adding a top-level CompositeField with FormActions in it.
  • A MajorActions button group is already provided as a default.
  • Drop ups with additional actions that appear as links are created via a TabSet and Tabs with FormActions inside.
  • A ActionMenus.MoreOptions tab is already provided as a default and contains some minor actions.
  • You can override the actions completely by providing your own getAllCMSFields.

Let's walk through a couple of examples of adding new CMS actions in getCMSActions.

First of all we can add a regular standalone button anywhere in the set. Here we are inserting it in the front of all other actions. We could also add a button group (CompositeField) in a similar fashion.

$fields->unshift(FormAction::create('normal', 'Normal button'));

We can affect the existing button group by manipulating the CompositeField already present in the FieldList.

$fields->fieldByName('MajorActions')->push(FormAction::create('grouped', 'New group button'));

Another option is adding actions into the drop-up - best place for placing infrequently used minor actions.

$fields->addFieldToTab('ActionMenus.MoreOptions', FormAction::create('minor', 'Minor action'));

We can also easily create new drop-up menus by defining new tabs within the TabSet.

$fields->addFieldToTab('ActionMenus.MyDropUp', FormAction::create('minor', 'Minor action in a new drop-up'));

Empty tabs will be automatically removed from the FieldList to prevent clutter.

To make the actions more user-friendly you can also use alternating buttons as detailed in the CMS Alternating Button how-to.

React-rendered UI

For sections of the admin that are rendered with React, Redux, and GraphQL, please refer to the introduction on those concepts, as well as their respective How-To's in this section.

Implementing handlers

Your newly created buttons need handlers to bind to before they will do anything. To implement these handlers, you will need to create a LeftAndMainExtension and add applicable controller actions to it:

namespace App\Extension;

use SilverStripe\Admin\LeftAndMainExtension;

class CustomActionsExtension extends LeftAndMainExtension
    private static $allowed_actions = [

    public function sampleAction()
        // Create the web

The extension then needs to be registered:

    - App\Extension\CustomActionsExtension

You can now use these handlers with your buttons:

$fields->push(FormAction::create('sampleAction', 'Perform Sample Action'));


In a few lines of code, we've customised the look and feel of the CMS.

While this example is only scratching the surface, it includes most building blocks and concepts for more complex extensions as well.