---
title: "TYPO3 Application context: Development or Production"
manual: "Getting Started"
version: "main"
permalink: "https://docs.typo3.org/permalink/t3start:application-context@main"
source: "Installation/ApplicationContext.rst"
modified: "2026-09-15T08:44:38+00:00"
---

# TYPO3 Application context: Development or Production

![Screenshot showing the current application context in the "System Information" box](_ApplicationContext/ApplicationContextInformation.png)

A TYPO3 instance is often used in different contexts that can adapt to your
needs.

You can use the application context to differentiate between different
environments / servers.

There are 3 major application context groups:

-   **`Development`**

    To be used during development. Debugging is enabled by default.

-   **`Production`**

    Debugging and deprecation logs are deactivated by default.

-   **`Testing`**

    To be used in automated testing.

You can define arbitrary strings as a subcontext for example `Development/Local`
or `Production/Stage`.

-   [Setting the application context](https://docs.typo3.org/permalink/t3start:setting-the-application-context@main)
-   [Local development](https://docs.typo3.org/permalink/t3start:local-development@main)
-   [Production environment](https://docs.typo3.org/permalink/t3start:production-environment@main)

## Setting the application context

If the application context is not set it is `Production` by default so that you
don't have to do anything on the production server.

In DDEV you should set the application context to `Development/Local` to enable
debugging and different site configurations for DDEV and your live server.

Create a file called `docker-compose.context.yaml` in your `.ddev`
path with the following content:

**\[project root\]/.ddev/docker-compose.context.yaml**

```yaml
services:
  web:
    environment:
      - TYPO3_CONTEXT=Development/Local

```

Restart DDEV using

```bash
ddev restart
```

## Local development

When you [installed TYPO3 with DDEV](https://docs.typo3.org/permalink/t3start:install@main), DDEV automatically created
a file called `config/system/additional.php` for you. This file includes
server settings needed only during development, including:

-   A connection to the local database in DDEV
-   Configuration of Mailpit to enable debugging of emails
-   Image magic configuration so that images can be scaled and edited
-   Enabling enhanced error reporting

You should not [deploy](https://docs.typo3.org/permalink/t3start:deployment@main) this file to your production server
but create one just for the production server.
See section [Production environment](https://docs.typo3.org/permalink/t3start:production-settings@main)

## Production environment

It is not recommended to put credentials into a file that is kept under version
control. However, many other settings should be kept under version control.

We recommend putting all configuration containing credentials into a special
file that is not kept under version control and include it in your
`config/system/additional.php`.

Create a file called `config/system/credentials.php`:

**config/system/credentials.php**

```php
<?php

defined('TYPO3') or die();
$customChanges = [
  'BE' => [
    'installToolPassword' => 'some encrypted string',
  ],
  'DB' => [
    'Connections' => [
      'Default' => [
        'dbname' => 'my_db',
        'host' => 'localhost',
        'password' => '<secure password>',
        'user' => 'my_db_user',
      ],
    ],
  ],
  'SYS' => [
    'encryptionKey' => 'replace with generated encryption key',
  ],
];

```

> [!IMPORTANT]
> Add `config/system/credentials.php` to your `.gitignore` so that it
> is never put under version control.

You can now include this file in your
`config/system/additional.php`:

**config/system/additional.php**

```php
<?php

defined('TYPO3') or die();

$customChanges = [
];

$GLOBALS['TYPO3_CONF_VARS'] = array_replace_recursive($GLOBALS['TYPO3_CONF_VARS'], (array)$customChanges);
$file = realpath(__DIR__) . '/credentials.php';
if (is_file($file)) {
  include_once($file);
  $GLOBALS['TYPO3_CONF_VARS'] = array_replace_recursive($GLOBALS['TYPO3_CONF_VARS'], (array)$customChanges);
}

```

The following steps are needed for a secure production context:

-   [Generate a unique encryption key](https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/Security/GuidelinesIntegrators/InstallTool.html#security-encryption-key-generate)
    and put it in `$customChanges['SYS']['encryptionKey']` in your
    `config/system/credentials.php`.
-   Choose a new install tool password and put its hash into
    `$customChanges['BE']['installToolPassword']`.
-   Replace the database credentials in the
    `$customChanges['DB']['Connections']['Default']` section with
    database credentials for your server.

Further settings important for security can be made directly in the
`config/system/additional.php`:

**config/system/additional.php**

```php
<?php

defined('TYPO3') or die();

$customChanges = [
  'BE' => [
    'debug' => '0',
  ],
  'FE' => [
    'debug' => '0',
  ],
  'SYS' => [
    'trustedHostsPattern' => 'SERVER_NAME', // keep this if it is working on your server
    'devIPmask' => '127.0.0.1,::1', // localhost oly
    'displayErrors' => 0, // Turn off error reporting
  ],
];

$GLOBALS['TYPO3_CONF_VARS'] = array_replace_recursive($GLOBALS['TYPO3_CONF_VARS'], (array)$customChanges);
$file = realpath(__DIR__) . '/credentials.php';
if (is_file($file)) {
  include_once($file);
  $GLOBALS['TYPO3_CONF_VARS'] = array_replace_recursive($GLOBALS['TYPO3_CONF_VARS'], (array)$customChanges);
}

```

Please refer to the security guide in getting started to check which settings
are currently recommended for a secure production environment:

[Global TYPO3 configuration options](https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/Security/GuidelinesIntegrators/GlobalTypo3Options.html#security-global-typo3-options)

Suggested configurations might change in future security bulletins.

You can put any of the suggested changes into the `$customChanges` array of
your `config/system/additional.php`.