---
title: "Feature toggle API"
manual: "TYPO3 Explained"
version: "13.4"
permalink: "https://docs.typo3.org/permalink/t3coreapi:feature-toggles@13.4"
source: "ApiOverview/FeatureToggleApi/Index.rst"
rendered: "2026-09-17T15:24:38+00:00"
---

# Feature toggle API {#feature-toggle-api}

TYPO3 provides an API class for creating so-called "feature toggles". Feature
toggles provide an easy way to add new implementations of features next to their
legacy version. By using a feature toggle, the integrator or site administrator
can decide when to switch to the new feature.

The API checks against a system-wide option array within
`$GLOBALS['TYPO3_CONF_VARS']['SYS']['features']` which an integrator or
admininistrator can set in the `config/system/settings.php` file. Both
TYPO3 Core and extensions can provide alternative functionality for a certain
feature.

Examples for features are:

-   Throw exceptions in new code instead of just returning a string message as
    error message.
-   Disable obsolete functionality which might still be used, but slows down the
    system.
-   Enable alternative "page not found" handling for an installation.

****Table of Contents****

-   [Naming of feature toggles](https://docs.typo3.org/permalink/t3coreapi:naming-of-feature-toggles@13.4)
-   [Using the API as extension author](https://docs.typo3.org/permalink/t3coreapi:using-the-api-as-extension-author@13.4)
-   [Core feature toggles](https://docs.typo3.org/permalink/t3coreapi:core-feature-toggles@13.4)
-   [Enable / disable feature toggle](https://docs.typo3.org/permalink/t3coreapi:enable-disable-feature-toggle@13.4)
-   [Feature toggles in TypoScript](https://docs.typo3.org/permalink/t3coreapi:feature-toggles-in-typoscript@13.4)
-   [Feature toggles in Fluid](https://docs.typo3.org/permalink/t3coreapi:feature-toggles-in-fluid@13.4)

## Naming of feature toggles {#naming-of-feature-toggles}

Feature names should NEVER be named "enable" or have a negation, or contain
versions or years. It is recommended to use "lowerCamelCase" notation for the
feature names.

Bad examples:

-   `enableFeatureXyz`
-   `disableOverlays`
-   `schedulerRevamped2018`
-   `useDoctrineQueries`
-   `disablePreparedStatements`
-   `disableHooksInFE`

Good examples:

-   `extendedRichtextFormat`
-   `nativeYamlParser`
-   `inlinePageTranslations`
-   `typoScriptParserIncludesAsXml`
-   `nativeDoctrineQueries`

## Using the API as extension author {#using-the-api-as-extension-author}

For extension authors, the API can be used for any custom feature provided by an
extension.

To register a feature and set the default state, add the following to the
[`ext_localconf.php`](../../ExtensionArchitecture/FileStructure/ExtLocalconf.md#file-extension-ext-localconf-php) file of your extension:

**EXT:some_extension/ext_localconf.php**

```php
$GLOBALS['TYPO3_CONF_VARS']['SYS']['features']['myFeatureName'] ??= true; // or false;
```

To check if a feature is enabled, use this code:

**EXT:some_extension/Classes/SomeClass.php**

```php
use TYPO3\CMS\Core\Configuration\Features;

final class SomeClass {
    public function __construct(
        private readonly Features $features,
    ) {
    }

    public function doSomething(): void
    {
        if ($this->features->isFeatureEnabled('myFeatureName') {
            // do custom processing
        }

        // ...
    }
}
```

> [!WARNING]
> **Attention**
>
> Currently, only the Core features can be (de-)activated in the Install Tool.
>
> To change the setting for your extension feature either use
> `config/system/settings.php` or `config/system/additional.php`
> files like:
>
> **config/system/additional.php | typo3conf/system/additional.php**
>
> ```php
> $GLOBALS['TYPO3_CONF_VARS']['SYS']['features']['myFeatureName'] = true;
> ```

The name can be any arbitrary string, but an extension author should prefix the
feature with the extension name as the features are global switches which
otherwise might lead to naming conflicts.

## Core feature toggles {#core-feature-toggles}

Some examples for feature toggles in the TYPO3 Core:

-   `redirects.hitCount`: Enables hit statistics in the redirects backend module
-   `security.backend.enforceReferrer`: If on, HTTP referrer headers are enforced
    for backend and install tool requests to mitigate potential same-site
    request forgery attacks.

## Enable / disable feature toggle {#enable-disable-feature-toggle}

Features can be toggled in the **Admin Tools > Settings** module via
**Feature Toggles**:

![Feature toggles in the Admin Tools](../../Images/ManualScreenshots/AdminTools/FeatureToggles.png)

Internally, the changes are written to `config/system/settings.php`:

**config/system/settings.php**

```php
'SYS' => [
    'features' => [
        'redirects.hitCount' => true,
    ],
]
```

> [!NOTE]
> <!-- TODO: no Markdown rendering for "versionadded" -->
>
> If the `config/system/settings.php` file is write-protected an info
> box is rendered. In that case, all input fields are disabled and the save
> button is not available.

## Feature toggles in TypoScript {#feature-toggles-in-typoscript}

One can check whether a feature is enabled in TypoScript with the function
`feature()`:

**EXT:some_extension/Configuration/Sets/SomeExtension/setup.typoscript**

```typoscript
[feature("unifiedPageTranslationHandling")]
    # This condition matches if the feature toggle "unifiedPageTranslationHandling" is true
[END]
```

## Feature toggles in Fluid {#feature-toggles-in-fluid}

<!-- TODO: no Markdown rendering for "versionadded" -->

A new condition-based Fluid ViewHelper was added. It allows
integrators to check for feature flags from within Fluid templates.

The [Feature ViewHelper \<f:feature>](https://docs.typo3.org/other/typo3/view-helper-reference/13.4/en-us/Global/Feature.html#typo3-fluid-feature) can be used to check for a feature in a Fluid
template:

**EXT:my_extension/Resources/Private/Templates/SomeTemplate.html**

```html
<f:feature name="unifiedPageTranslationHandling">
   This is being shown if the flag is enabled
</f:feature>
```