The latest version, WordPress 4.0, has been released to the public. The information below describes a Five-Step upgrade process and a more detailed upgrade process. Please follow one these guideline to upgrade to the WordPress Version 4.0.
Read the Detailed Upgrade Instructions if you want more intricately scripted steps!!!
Upgrading WordPress can be a little tricky, but fear not, this guide will help make quick work of upgrading your jazzed-up WordPress! This process will provide pointers to protect you against disasters (other software providers might call "user errors").
Before starting, you need to understand WordPress is easy to upgrade. Preserving any customizations you might have made is what makes this a 5-step process instead of 3-step one. It would be nice to believe this is a 5-minute process, but the part about backing up your data and file might take a little more than 5 minutes if you are a prolific blogger.
The steps to a healthy upgrade are as follows:
Let us assume your blog has a URI like http://example.com/wordpress/.
Here, the objective is to save the data, and your customizations.
Basically, save the files that you have changed or added since you installed the standard WordPress. Use an FTP tool to download a copy of all the files on the server, in the directory where you installed WordPress, including the .htaccess files if you have been playing with it. Backup at least the .htaccess file, the files used by your current theme (which will be in the /wp-content/ directory), the /wp-images/ directory with your uploaded images and files, any WordPress core files that you modified to use some "hack" directory, and the wp-config.php file which contains your database username, password etc.
Deactivate all the Plugins you use at the Plugin Management Page ( http://example.com/wordpress/wp-admin/plugins.php ). Some Plugins might not work with WordPress 4.0, and that is why you want to deactivate them all. This will ensure that you don't end up with an upgraded-but-broken installation of WordPress after the upgrade process.
Get the latest and greatest WordPress and upload it to the WordPress directory, overwriting all the files that exist there. This will preserve your images and themes. What if something goes wrong, you ask? Well, did you not create a backup of all files in Step 1? You can fall back upon them in the worst case scenario.
Visit your blog's Upgrade Page ( http://example.com/wordpress/wp-admin/upgrade.php ) and follow the instructions that are displayed.
Awaken the monsters, one by one, at the Plugin Management Page ( http://example.com/wordpress/wp-admin/plugins.php ). Check if everything works as expected. There is a list of Plugins that are known to work with WordPress 2.0 here. If some Plugins do not work, deactivate the plugin, then contact the plugin author to encourage the author to upgrade the plugin.
There, that does it.
Something went wrong, you say? No worries. Since you backed everything up earlier, restore the files and database tables you backed up, and this time, consider following the Detailed Instructions below.
Important Note: if you haven't completed the steps above, do not attempt the upgrade.
wp-contentfolder; Special Exception: the
wp-content/cachefolder should be deleted.
wp-includes/languages/folder--if you are using a language file do not delete that folder;
.htaccessfile--if you have added custom rules to your
.htaccess, do not delete it.
That's the overview of the upgrade process. Please continue reading the Detailed Upgrade Instructions.
Remember, if you do encounter problems, re-read the Instructions below to insure you've followed the proper procedures and consult Troubleshooting: Common Installation Problems.
The following are the instructions that explain the above steps in more detail. Please read all of the instructions before starting.
Perform a backup of your database. All of your WordPress data, such as Users, Posts, Pages, Links, and Categories, are stored in your MySQL database. Please read Backing Up Your Database for a detailed explanation of this process.
It is extremely important to back up your database before beginning the upgrade. If, for some reason, you find it necessary to revert back to the 'old' version of WordPress, you may have to restore your database from these backups.
Back up ALL of your files in your WordPress directory and your .htaccess file. Typically, this process involves using an FTP program to download ALL your WordPress files from your host to your local computer. Please read Backing Up Your WordPress Site for further explanation.
If you have made changes to any core WordPress files, or if you've got customized Plugins or Themes, you will want to have a good backup of those files. It is extremely important to back up your files before beginning the upgrade. If for some reason you find it necessary to revert back to the 'old' version of WordPress you will need to upload these files.
Verify that the backups you created are there and usable. This is the most important step in the upgrade process! The verification process involves making sure you can see the backup files on your local computer (or wherever you've stored them) and that you can navigate into any sub-folders. If the files are in a zip file, make sure you can open the zip file.
In your Administration panel, under the Plugins choice, deactivate any Plugins. Because of the changes to WordPress, some Plugins may conflict with the upgrade process.
If you have not completed the first four procedures, STOP, and do them! Do not attempt the upgrade unless you have completed the first four steps.
The best resource for problems with your upgrade is the WordPress Support Forums, and if you have problems, the volunteers at the WordPress Support Forums will likely ask if you have completed the first four steps.
Download and unzip the WordPress package from http://wordpress.org/download/.
The WordPress package will be extracted into a folder called wordpress.
Why Delete? Generally, it is a good idea to delete whatever is possible because the uploading (or upgrading through cPanel) process may not correctly overwrite an existing file and that may cause problems later.
DO NOT DELETE these folders and files:
wp-includes/languages/folder--if you are using a language file, do not delete this folder;.
.htaccessfile--if you have added custom rules to your
.htaccess, do not delete it;
wp-contentfolder, do NOT delete them.
Delete these Files and Folders:
wp-* (except for those above), readme.html, wp.php, xmlrpc.php, and license.txt;files; Typically files in your root or wordpress folder. Again, don't delete the
wp-includesfolder; If using a language file remember don't delete the
wp-content/cachefolder; You only see this folder if you are upgrading FROM WordPress 2.0.
How to Delete? There are several ways to delete the files from your WordPress site. You can use your FTP Client, or if you have access to Telenet or SSH you can use that. Some host providers also provide the ability to delete files and folders.
cp wp-config.php .htaccess wp-layout.css index.php wp-comments.php wp-comments-popup.php backup
cp -R wp-content backup
rm wp*.php wp-layout.css .htaccess license.txt readme.html xmlrpc.php
rm -rf wp-admin wp-includes
cp backup/wp-config.php .
With the new upgrade on your local computer, and using FTP, upload the new files to your site server just as you did when you first installed WordPress. See Using FileZilla and Uploading WordPress to a remote host for detailed guidelines in using an FTP Client to upload.
NOTE: If you did not delete the
wp-content folder, you will need to overwrite some files during the upload.
wp-content folder holds your WordPress Themes and Plugins. These should remain. Upload everything else first, then upload only those WordPress files that new or changed to your new
wp-content folder. Overwrite any old versions of default plugins with the new ones.
The WordPress default theme has changed so you will want to upload the
wp-content/themes/default folder. If you have custom changes to the default theme, those changes will need to be reviewed and installed after the upgrade.
Run the WordPress upgrade script by accessing wp-admin/upgrade.php in your favorite web browser and follow the instructions presented on your screen.
In your Options->Permalinks panel update your Permalink Structure and, if necessary, place the rules in your .htaccess file. Also see Using Permalinks for details regarding Permalinks and the .htaccess file.
Please review the list of Plugins that work in Version 2.0. You will want to upload and install any new versions of your Plugins and Themes. Check with the author of those Plugins and Themes for the updated versions.
Use your Administration Panel, Plugins, to activate your Plugins.
Please note that if you are using the new WordPress Database Backup Plugin you may need to change the permissions on your
wp-content folder to make it writeable by your webserver (either mode 666 or even 777). See Changing File Permissions for more details.
As of now, there is no official list in Codex that describes all the new features, but look at these resources:
If you are considering upgrading to WordPress Version 2.0.1, but you are at Version 1.2, then follow the 1.2 to 1.5 upgrade as describe in Upgrading From WordPress Version 1.2 to 1.5. Once you are upgraded to Version 1.5.x, then follow the instructions as listed above to upgrade from 1.5 to 2.0.1.