Upgrading from XOOPS 2.0.* above 2.0.14 and 2.2.* (using the full package)
0. Unpack the archive to your LOCAL computer (e.g. PC) in a temporary directory.
1. Move the "upgrade" folder inside the "htdocs" folder (it's been kept out as it's not needed for full installs) on your local computer
2. Delete htdocs/mainfile.php, htdocs/install/, htdocs/cache/, htdocs/template_c/, htdocs/themes/ and htdocs/uploads/ from the "htdocs" folder on your LOCAL computer
* if you have created XOOPS_TRUST_PATH folder on your server, copy the content of /xoops_lib to that directory, and delete /xoops_lib from the "htdocs" folder on your LOCAL computer
3. Upload the content of the /htdocs folder on your LOCAL computer over your existing files on your server
4. For security considerations, you are encouraged to move directories xoops_lib (for XOOPS libraries) and xoops_data (for XOOPS data) out of Document Root, and change the folder names.
5. Make the directory of xoops_data/ writable; Create and make the directories of xoops_data/caches/, xoops_data/caches/xoops_cache/, xoops_data/caches/smarty_cache/ and xoops_data/caches/smarty_compile/ writable.
6. Ensure the server can write to mainfile.php
7. If you have Protector previously installed, open the "mainfile.php" file , and remove the Pre-check and Post-check lines (if they exist):

include XOOPS_TRUST_PATH.'/modules/protector/include/precheck.inc.php' ;
include XOOPS_TRUST_PATH.'/modules/protector/include/postcheck.inc.php' ;

8. Access <your.site.url>/upgrade/ with a browser, and follow the instructions
9. Follow the instructions to update your database
10. Write-protect mainfile.php again (permission 0444 on Linux)
11. Delete the "upgrade" folder from your server
12. Update the "system" module from the modules administration interface, other modules are recommended to update as well

Upgrading a non UTF-8 site:
UTF-8 encoding has been introduced into XOOPS 2.3 as default charset. However, there might be some problems with converting existing websites from non UTF-8 charset to UTF-8.
Before there is a good enough solution for this conversion, following settings are recommended when you upgrade an existing website (if you are not an experienced user):
- Select "Do not change" option in "Database character set and collation" step during upgrade process
- Modify /languages/yourlanguage/global.php to use your previous _CHARSET value if it has been changed to UTF-8 in your new global.php file as

define('_CHARSET', 'UTF-8');