To gain access to a TYPO3 backend when you don't have a working set of credentials, you might either try using a MySQL client and directly add the user to the database, but this is kind of unwieldy.

It's easier to use the TYPO3 install tool.

On a proper install the install tool can be accessed via <yourdomain.name>/typo3/install from your browser, where you will be prompted for the install password. Since it is extremely likely that you do not know it anymore, change it to one you know. Also the install tool is very likely deactivated. TYPO3 may tell you in the login mask, which file to create on the server so you can access the web interface afterwards. For me it was to create an empty file called ENABLE_INSTALL_TOOL in the typo3conf folder of the typo3 install.

To get a working password, you have to swap the md5 hash of the password in the <path-to-your-typo3-install>/typo3conf/localconf, or in TYPO3 versions prior to 6.0 in the localconf.php file. Have a look at the TYPO3 documentation what to do exactly, as this can change with new TYPO3 releases.

Sidenote:

To get a working hash, simply enter the password you want in to the install tool webmask. The login will fail and the tool will tell you the hash of the password you wanted to use.

Once you are logged in, choose the 'Database Analyser' menu, in there you should be able to create a new 'admin' user.

With that one you can login into the backend.

Do not forget to cleanup after you (remove the ENABLE_INSTALL_TOOL file from the typo3conf folder).

This article is derived from typo3: access without password by sjas and is licensed under a CC BY-SA 3.0 license.