Updating the vBulletin Scripts on Your Web Server 
After downloading the latest version of vBulletin, you will need to decompress the package into a directory on your local workstation. Once this is completed you can start the upgrade process.
1To begin, you will want to turn off your forums. This will help eliminate any potential db errors as people attempt to access your forums before the upgrade is complete. For more information on how to do this, see the Turn Your vBulletin On and Off article.
2Once your vBulletin site is turned off, you can upload the files. We're using Filezille in the following steps.
3Connect to your SFTP server.
4Navigate to the new vBulletin files (on your local machine) in the local pane and the existing old files in the remote pane.
5Upload the local files into over the files of your remote vBulletin installation as shown here, overwriting the files currently in place:

At this point, you will be prompted by the FTP client to confirm that you want to overwrite the existing files. You should confirm this prompt, telling the FTP client that yes, you do want to overwrite the existing files. If the prompt gives you the option to overwrite all existing files without prompting again, use this option.

Upgrading from vBulletin 3.8.11 or vBulletin 4.2.5

If you are upgrading from a legacy version of vBulletin, it is required that you put the vBulletin files in a new directory. to delete all previous vBulletin files from the server before uploading the vBulletin files. Special care should be used to maintain the directories with user uploaded content like avatars and attachments. The directory structure and file layout in vBulletin has changed dramatically and this will make sure there are no conflicts between files.
Most FTP client applications will handle the file transfers automatically, but if for some reason your application does not, you should make a note of the following:
If you installed vB5 directly in the root directory of your web publishing folder (not in a subfolder), you should upload all the files contained in the upload folder directly into the web publishing folder on the server, overwriting the files directly.
It is extremely important that you upload all the files from the latest vBulletin package, including the entire contents of the install directory (except the install.php file).

Failure to upload all the files may result in the upgrade script being unable to successfully complete the upgrade process.
Shane 20th Apr 2005, 11:00am
Do not use a Browser FTP function. It allows for to many mistakes during upload. Use a dedicated FTP program.
StewardManscat 20th Apr 2005, 11:06am
Remember to rename/replace your admin subdirectories... if you were foolish enough to follow the advice about renaming them for security purposes in the first place. The original directories are called admincp and modcp.
Retro 30th Sep 2005, 11:13pm
Using FlashFXP, make sure you have your File Exist Rules set to overwrite any files that already exist, regardless of size.

<Added note by Floris>
The same goes for many ftp clients, make sure you have it set to overwrite files, do not skip or resume files while uploading!
Mike Pepper 27th May 2007, 09:44am
Alternative (3rd) method to shorten server downtime.

Upload to a temporary copy of your vB production directory, then when the upload is complete, switch the directories and continue from there.

The actual upload, after you've prepared the files, is the longest part of the server downtime. The objective with this method is to complete the upload of new files before you have to take down ("turn off") your forums.

Here are the steps:

1. Complete all file preparation as per the previous step, "Preparing the vBulletin files for Upload".

Then, before you upload any files go to step 2 here.

2. On your production server, COPY the entire vBulletin directory (or "folder") structure to another temporary directory. Be sure to preserve all attributes of ownership, permissions, etc.

For example, if your vB forums are in a directory called "vbbs", then you might copy it to one called "vbbsupdate". Your forums in "vbbs" will keep running for now.

On *ix at the command line use (e.g.)
"cp -pr vbbs vbbsupdate"

3. Upload your prepared vB update files to your temporary "vbbsupdate" directory as described above in the "overwrite" method.

REPEAT: upload to your temporary directory; in this example the one called, "vbbsupdate".

4. Wait till the wee hours of the morning to minimize impact on your traffic.

5. Turn off your forums in the admin CP.

6. Back up your database so that the backup is as fresh as possible.

7. Switch the directories by first renaming your (e.g.) "vbbs" directory to "vbbsold" and then renaming your "vbbsupdate" directory to "vbbs" (changing the names to match your setup, of course).

8. Run the update script as described in the next step, "Running the vBulletin Upgrade Script".

Good luck. The few times that I've done it, it runs pretty smoothly.
Schnee 30th Jun 2008, 06:17am
Don't delete your own favicon or you will get the VBulletin one back again.
A.I.Smari 09th Jul 2008, 07:49am
If you're upgrading from a very recent version, you may consider deleting all gif/jpg files locally to save on your upload time.
Windsun 09th Sep 2008, 06:22am
Just for the information, you can also use Microsoft Expression Web 2.0 in ftp mode to upload files.
Welshy 02nd Feb 2010, 02:28pm
The SmartFTP shown in the sample above is an OLD Version.

The "Overwrite" has been long since, dropped. This was confirmed to me by "mb" the creater and owner of SmartFTP.

He recommended that we use the "Merge" option.

Can anyone tell me, that uses the SmartFTP, if they use the 'Merge' to upgrade their forum, Please? (Ie: I need upgrade my 3.8.1 to 3.8.4 PL2, and I do not want to lose any info on my database etc).

Thanks for your input.
klancy 04th Apr 2010, 03:24pm
"Before you do this you should close your forums."

It might sound silly, but it's good to link actionable instruction sentences if those instructions are defined somewhere else. (I used to write help sections for a big site.) Surprisingly enough, even what appears like simple instructions will get a lot of clicks.

I am pointing this out as a general guideline since I've seen it in more than once place on this site. (opportunities to link so people don't have to hunt)
Stewart Whitfield 04th Apr 2010, 03:24pm
I use SmartFTP and I use the merge function quite successfully.
Chris 14th Apr 2016, 03:09am
Won't following the above instructions result in overwriting config.php. a file that has been modified with site variables. That is not desirable is it?
Trevor Hannant 14th Apr 2016, 03:16am
Chris, the second 'Note' section states:

"If you are upgrading from one version of vBulletin 5 to another 5.x version, you should also delete the config.php.bkp and core/includes/config.php.new files."