Calls to deprecated functions are logged to track usage of deprecated/outdated methods in the TYPO3 Core. Developers have to make sure to adjust their code to avoid using this old functionality since deprecated methods will be removed in future TYPO3 releases.

Deprecations use the PHP method trigger_error('a message', E_USER_DEPRECATED) and run through the logging and exception stack of the TYPO3 Core. There are several methods that help extension developers in dispatching deprecation errors. In the development context, deprecations are turned into exceptions by default and ignored in the production context.

Enabling deprecation errors

TYPO3 ships with a default configuration, in which deprecation logging is disabled. If you upgrade to the latest TYPO3 version, you need to change your development configuration to enable deprecation logging in case you need it.


Enabling the deprecation log can be done in the Admin Tools > Settings backend module. Click on Choose Preset in the Configuration Presets pane, open Debug settings, activate the Debug option and submit with Activate preset. Disabling the deprecation log can be done by selecting the Live preset instead.

Enabling the debug preset

Enabling the debug preset

The debug preset enables also some other debug settings.

Via configuration file directly

Instead of using the GUI you can also enable or disable the deprecation log with the disabled option:

Excerpt of config/system/settings.php | typo3conf/system/settings.php

return [
    // ... some configuration
    'LOG' => [
        'TYPO3' => [
            'CMS' => [
                'deprecations' => [
                    'writerConfiguration' => [
                        'notice' => [
                            'TYPO3\CMS\Core\Log\Writer\FileWriter' => [
                                'disabled' => false,
    // ... more configuration

Deprecation logging can also be enabled in the additional.php configuration file, here with safeguarding to only enable it in development context:

config/system/additional.php | typo3conf/system/additional.php

use Psr\Log\LogLevel;
use TYPO3\CMS\Core\Core\Environment;
use TYPO3\CMS\Core\Log\Writer\FileWriter;

if (Environment::getContext()->isDevelopment()) {
    ['disabled'] = false;

For more information on how to configure the writing of deprecation logs see Writer configuration.

Find calls to deprecated functions

The extension scanner provides an interactive interface to scan extension code for usage of removed or deprecated TYPO3 Core API.

It is also possible to do a file search for @deprecated and E_USER_DEPRECATED. Using an IDE you can find all calls to the affected methods.

The deprecations are also listed in the changelog of the corresponding TYPO3 version.

Deprecate functions in extensions

Methods that will be removed in future versions of your extension should be marked as deprecated by both the doc comment and a call to the PHP error method:

Excerpt of EXT:my_extension/Classes/MyClass.php
 * @deprecated since version 3.0.4, will be removed in version 4.0.0
public function decreaseColPosCountByRecord(array $record, int $dec = 1): int
        'Method "decreaseColPosCountByRecord" is deprecated since version 3.0.4, will be removed in version 4.0.0',

    // ... more logic

For more information about how to deprecate classes, arguments and hooks and how the TYPO3 Core handles deprecations, see How to deprecate classes, methods, arguments and hooks in the TYPO3 core.