Your WordPress is not running? How to fix the most common mistakes!

Any WordPress user who dips something into the code or likes to reinstall or change plugins and themes knows the problem. Inevitably, at some point an error appears. It can be very frustrating if you do not have a solution immediately. But other WordPress users before you already had the same problems and have solved them. Benefit from the following solutions for the most common WordPress errors.

Error # 1 | Warning: Can not modify header information – headers already sent by

Warning: Can not modify header information – headers already sent by (output started at /path/blog/wp-config.php:34)

This error usually shows your browser directly after a WordPress update or a modification to a WordPress file via the editor.

The solution after an update:

  1. Delete blanks, superfluous lines and the like in thewp-config.php
  2. Download thewp-config.phpdown to your computer via FTP
  3. Open thewp-config.phpin a text editor / development environment
  4. Delete all spaces before the opening onephp-Element
  5. Make sure there are no characters or spaces in front of the php element

Make sure there are no characters before the opening PHP character.

At the bottom of thewp-config.phpThere should not be a closing PHP character. If there is one, please delete all spaces and empty lines.

Delete the closing PHP character including all blank lines / characters

Gladly this error also appears, if one changes with the editor in the WordPress administration a file.

Solution after an editor file change:

  1. Download the modified file via FTP to your computer.
  2. Undo the change
  3. Upload the file back to your webspace with FTP – now everything should work again.
  4. Once everything works again, change the file again and upload it again using FTP

This error can always be caused by files other than wp-config.php.In any case, read the error message carefully, it tells you where and in which file you need to search.

Error # 2 | Your WordPress blog and administration interface will only show white pages

Most of the time, this problem occurs immediately after a WordPress update, after a theme installation or plug-in installation. The entire website, including the admin section, only displays white pages and gives you every opportunity to get to the dashboard to fix the error.

After a WordPress update or theme installation, your website will only show white pages.

Solution after a theme installation:

Renaming the current theme folder via FTP will cause WordPress to use the default theme. Then you should have access to the WordPress administration interface again.

1. Navigate via FTP towp-content / themesFolder structure.

Navigate via FTP to the wp-content / themes folder structure

2. Next, rename your current theme by typing-tempappend to the file name.

Rename the current theme

3. Log in to your website (wp-admin)

4. Make sure your desired theme is compatible with this WordPress version (which you use).

5. Check if your theme contains code that can not be executed.

Solution after a plugin installation:

Reset the plugin folder via FTP

1. Navigate towp-contentFolder and name the folder inplugins-temparound

Rename the plugin folder from WordPress to plugins-temp

2. Create a new folder calledpluginsunderwp-content

3. Now try logging into your dashboard (wp-admin)

4. Move your plugins from the folderplugins-tempin the newly created folderplugins

5. Now activate one plugin after the other and check each time, whether your website is still reachable or works flawlessly

6. Also check if one of your plugins is not compatible with the version of WordPress you are using.

If the error happened after a WordPress update, play back your backup made before the update.

Error # 3 | Fatal error: Allowed memory size of 33554432 bytes exhausted

Often you get the following error message “Fatal error: Allowed memory size of 33554432 bytes exhausted“After trying to upload a medium sized graphics file.

To solve this error, you need to increase the PHP memory limit. For example, the memory limit can be set to the following values: 32MB, 64MB, 128MB or 256MB. The following solutions are available for this:

The solutions:

Solution 1:Edit your .htaccess file

Paste the following code into your .htaccess file:

php_value memory_limit 64M

Solution 2:Edit your wp-config.php

define ('WP_MEMORY_LIMIT', '64M');

Solution 3:Create a PHP.ini file in the wp-admin folder

  1. Open a text editor (Notepad on Windows, TextEdit on Mac)
  2. Paste the following code:memory_limit = 64M
  3. Save the file as PHP.ini
  4. Upload the file via FTP to the wp-admin folder

If none of the solutions presented here work, contact your hosting provider to have the PHP memory limit raised.

Error # 4 | Fatal error undefined function is_network_admin ()

The error message “Fatal error undefined function is_network_admin ()“You sometimes get when you try to log into your admin area after a WordPress update.

The solution: A manual update

  1. Download the latest WordPress version and unzip it.
  2. Create a backup of your WordPress website including a database backup.
  3. Name the folderswp-includesandwp-admininwp-includes.bakandwp-ADMIN.BAKaround.
  4. Load the unpackedwp-includesandwp-adminFolder from the newly downloaded WordPress via FTP including all files contained in it up your server
  5. Now replace all WordPress files that are in the first level of your unzipped WordPress folder with the old files in the first level via FTP –just upload the individual files, not the folders
  6. Delete the file.maintenancefrom the top level of your WordPress installation on the server
  7. After signing in to the WordPress admin section, a similar link like this one should appear here:“Http://”, Follow the link and further instructions.
  8. If you are using a caching plugin, delete the cache to see changes.

More details about the manual WordPress update can be found in the manual update instructions in the WordPress Codex.

Error # 5 | 404 after a theme installation

Especially after a theme installation likes to appear404 – Page not foundError. This is because some themes use custom post types, each of which registers its own permalinks. This sometimes confuses the complete WordPress structure of the links.

The solution:

The solution of the problem is quite simple. Navigate toSettings => permalinksAnd just save your existing structure again.

Save the existing permalink structure and the error is forgotten.

Save the existing permalink structure and the error is forgotten.

After you do that, the bug should be fixed.

Error # 6 | Internal Server Error after .htaccess update

The internal server error

The Internal Server Error – welcome after .htaccess modification.

This error most often occurs after a modification of the server control file .htaccess. It states that either instructions have not been correctly copied and pasted, or that functions are being driven that are not present or allowed on the server.

The solution: delete modifications again

The additions that led to the error should be deleted again. Then your website will be displayed correctly again. Now and then plugins can also cause this error because they need write access to this important file (for example WP Super Cache).

The solution after plugin error:

Log into your webhosting with an FTP program and delete them.htaccessFile. You can find them in the root directory of your WordPress installation.

You may need to enable the hidden files viewer in the FTP program to see this file.

Delete this file!

Delete this file!

After doing this, log into your WordPress and navigate toSettings => permalinks“. Save the settings again without modification. Now WordPress should be a new one.htaccessFile and your website should run flawlessly.

If this little trick does not help and you do not use it.htaccesscan generate, here comes the WordPress standard content:

					# BEGIN WordPressRewriteEngine On RewriteBase / RewriteRule ^ index \ .php $ - [L] RewriteCond% {REQUEST_FILENAME}! -F RewriteCond% {REQUEST_FILENAME}! -D RewriteRule. /index.php [L]# END WordPress

Always back up this important file before modifying your .htaccess file. A simple copy of the file is quite enough. Click on it with your mouse on the right and duplicate the file. Only then make changes to her. This will save you from bad surprises.

For all changes, make sure that you copy and paste the complete code from the snippets offered on the internet. Even a single missing character will cause the “Internal Server Error”.

Error # 7 | The WordPress Redirect Error

The effects are annoying: Often you can no longer log in to the admin area of your WordPress and get the error message that too many redirects – ie redirects – happen. Or you will be redirected to the previously existing domain / URL.

Whatever you do, access to the CMS is no longer possible.

This error can occur through changes to the domain, the URL structure, and by assigning an HTTPS certificate.

The solution of the problem:

The cause of the error: incorrect settings in the backend.

The cause of the error: incorrect settings in the backend.

If these settings are no longer correct, then the error will occur. You can fix it pretty easily. Log into your webhosting via FTP, download thewp-config.phpto your computer and insert the following constants into the file:


Du musst natürlich noch deine korrekte URL eingeben. Wenn du die wp-config.php nicht aktualisieren möchtest oder kannst, dann gäbe es noch die Möglichkeit, die functions.php deines Themes für die Änderung zu verwenden.

Füge dort folgendes ein:


Nach diesen kleinen Änderungen hast du sofort wieder Zugriff auf deine Website und kannst dich auch problemlos einloggen. Ich empfehle, zuvor noch den Browser-Cache zu löschen, denn ansonsten könnte sich der Fehler noch im Browser befinden und dich in den Wahnsinn treiben.

(Der Artikel erschien erstmals am 9. August 2012 und wird seitdem regelmäßig aktualisiert, zuletzt am 20. Februar 2019.)

(Beitragsbild: Depositphotos)