Pages of a website hosted in Plesk fail to load: Size of a request header field exceeds server limit

1. Connect to the Plesk server via SSH.

2. Create a backup of the Apache configuration file:

   # cp -a /etc/httpd/conf/httpd.conf /root/httpd.conf_`date +%F`

3. Open the file in a text editor. In this example, we are using the vi editor:

   # vi /etc/httpd/conf/httpd.conf

4. Add the following line and specify your value (16000 is an example):

   LimitRequestFieldSize 16000

5. Save the changes and close the file.

6. Restart the Apache service to apply the changes:

   # service httpd restart

   Note: In case the value of 16000 (16KB) is not enough, increase it to the greater value, for example, 32000 (32KB).

1. Connect to the Plesk server via SSH.

2. Create a backup of the Apache configuration file:

   # cp /etc/apache2/apache2.conf /etc/apache2/apache2.conf_`date +%F`

3. Open the file in a text editor. In this example, we are using the vi editor:

   # vi /etc/apache2/apache2.conf

4. Add the following line and specify your value (16000 is an example):

   LimitRequestFieldSize 16000

5. Save the changes and close the file.

6. Restart the Apache service to apply the changes:

   # service apache2 restart

   Note: In case the value of 16000 (16KB) is not enough, increase it to the greater value, for example, 32000 (32KB).

If the website is using nginx-only hosting, apply the following steps:

1. Log in to Plesk.

2. Go to Domains > example.com > Hosting & DNS > Apache & nginx Settings.

3. Add the following line to Additional nginx directives then hit Apply.

   large_client_header_buffers 4 16k;

   Note: Edit 16k to match whatever request buffer size you need keeping in mind 8k is default, and the larger the buffer size the greater the impact from a DDOS attack.