you should first:doc:`upgrade to the last minor version</setup/upgrade_minor>`

(e.g. 4.4) so that you can see *all* the deprecations.

Deprecations in Web Debug Toolbar

To help you find deprecations, notices are triggered whenever you end up

using a deprecated feature. When visiting your application in the

:ref:`dev environment<configuration-environments>`

Deprecations in logs

If you use the Symfony default configuration, the deprecations are also logged in a ``prod.deprecations.log`` file (prod environment):

..code-block::yaml

Under the hood, deprecations are logged on the ``php`` Monolog channel at ``INFO`` psr-3 level. But as soon as an extra ``deprecation`` channel exists; deprecations are logged into this channel instead. So you can log deprecations on this dedicated channel and make the ``deprecation_filter`` useless:

..code-block::yaml

..versionadded::5.1

The deprecation logging into a dedicated channel was introduced in Symfony 5.1.

Road to Code Deprecation Free

1. Track the deprecations from the PHPUnit bridge and/or (depending on your test coverage) browse your application and note the deprecations on the web debug toolbar.

2. Deploy your code (that should not have deprecations anymore) on production and check for a while that no remaining deprecations are logged into ``prod.deprecations.log``.

3. When you're sure there is no more deprecations, follow the steps below to upgrade your application.

.. _upgrade-major-symfony-composer:

2) Update to the New Major Version via Composer