The following sections contain hints to help you solve common problems. Note that you should also check the section “System Environment” in the Install Tool, in which TYPO3 will inform you about errors and warnings in your installation which might influence performance. Follow the advice given there to fix those issues. This helps to solve or prevent most issues.

During troubleshooting, in the “Configuration Presets” section of the Install Tool, under “Debug settings”, you should select the “Debug” preset. This is especially helpful, if e.g. in the Frontend you only see a blank page. With debug settings activated, the PHP error message will be displayed, which will help you narrow down the problem.


Some settings may require adjustment for TYPO3 to operate correctly.

Enable Necessary Modules

TYPO3 makes use of several Apache modules, two modules that will need to be enabled are mod_expires and mod_rewrite. Apache modules can be enabled by editing your http.conf file, locating the required module and removing the preceding hash symbol:

#LoadModule expires_module modules/
#LoadModule rewrite_module modules/

Adjust ThreadStackSize on Windows

If you are running TYPO3 on top of Windows, the extension manager might not appear. Instead you might only see a blank screen in the right frame.

This problem is caused by the value of ThreadStackSize, which on Windows systems by default is set too low. To fix this, add the following lines at the end of your httpd.conf file:

<IfModule mpm_winnt_module>
  ThreadStackSize 8388608


Install Tool

The “System Environment” section of the Install Tool provides detailed information about any missing PHP modules and any other settings that may not be configured correctly.

For example, the PHP extensions openssl and fileinfo must be enabled. This can be achieved by adding (or uncommenting) the following lines in the [PHP] section of your php.ini file:

On a Windows-based server, these are the extension files:


PHP Caches, Extension Classes etc.

There are some situations which can cause what appear to be totally illogical problems after an upgrade:

  • If extensions override classes in which functions have changed. Solution: Try disabling all extensions and then enable them one by one until the error recurs.
  • If a PHP cache somehow fails to re-cache scripts: in particular, if a change happened to a parent class overridden by a child class which was not updated. Solution: Remove ALL cached PHP files (for PHP-Accelerator, remove /tmp/phpa_*) and restart Apache.


Character Set

TYPO3 uses UTF-8 encoding, you will need to ensure that your instance of MySQL also uses UTF-8. When installing TYPO3 for the first time, you can select UTF-8 encoding when you create the database for the first time. For an existing database, you will have to set each table and column to use UTF-8.


Cached Files in typo3temp/

Generally you should know that TYPO3 generates temporary “cached” files and PHP scripts in typo3temp/Cache/. You can remove the whole typo3temp/Cache directory at any time; the directory structure and all the caches will be re-written on the next hit to the system.

A shortcut to remove these caches can be found in the Install Tool, under “Important Actions”. This might be useful in the event your cache files become damaged and your system is not running correctly. The Install Tool won’t load any of these caches or any extension, so it should be safe to use regardless of the corrupt state of the Caches.

Amongst other caches, under typo3temp/Cache/Code/cache_core/ you find files like these:

-rw-rw----   1 www-data   www-data   61555  2014-03-26 16:28   ext_localconf_8b0519db6112697cceedb50296df89b0ce04ff70.php
-rw-rw----   1 www-data   www-data   81995  2014-03-26 16:28   ext_tables_c3638687920118a92ab652cbf23a9ca69d4a6469.php

These files simply contain all ext_tables.php and ext_localconf.php files of the installed extensions concatenated in the order they are loaded. Therefore including one of these files would be the same as including potentially hundreds of PHP files and should improve performance.

Concerning these files you have to consider the following:

  1. Making changes to these files does not make sense, because they can be removed and recreated from the “originals” at any time. You should instead change the “originals”.
  2. If you make changes to the original ext_tables.php or ext_localconf.php files in your extensions, you will have to clear the cached files away for your changes to take effect.

Possible Problems With the Cached Files

Changing the absolute path to TYPO3

If you change the path of the TYPO3 installation, you might get a lot of errors like “Failed opening …” or “Unable to access …”. The problem is that absolute file paths are hard-coded inside the cached files.

Fix: Clean the cache using the Install Tool: Go to “Important Actions” and use the “Clear all caches” function. Then hit the page again.

Changing Image Processing Settings

When you change the settings for Image Processing (in normal mode), you must take into account that old images may still be in the typo3temp/ folder and that they prevent new files from being generated! This is especially important to know, if you are trying to set up image processing for the very first time.

The problem is solved by clearing the files in the typo3temp/ folder. Also make sure to clear the database table “cache_pages”.