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B.3.2.4 Client does not support authentication protocol

The current implementation of the authentication protocol uses a password hashing algorithm that is incompatible with that used by older (pre-4.1) clients. Attempts to connect to a 4.1 or higher server with an older client may fail with the following message:

$> mysql
Client does not support authentication protocol requested
by server; consider upgrading MySQL client

To deal with this problem, the preferred solution is to upgrade all client programs to use a 4.1.1 or higher client library. If that is not possible, use one of the following approaches:

  • To connect to the server with a pre-4.1 client program, use an account that still has a pre-4.1-style password.

  • Reset the password to pre-4.1 style for each user that needs to use a pre-4.1 client program. This can be done using the SET PASSWORD statement and the OLD_PASSWORD() function. As of MySQL 5.6.6, it is also necessary to first ensure that the authentication plugin for the account is mysql_old_password:

    mysql> UPDATE mysql.user SET plugin = 'mysql_old_password'
    mysql> WHERE User = 'some_user' AND Host = 'some_host';
        -> 'some_user'@'some_host' = OLD_PASSWORD('new_password');

    Substitute the password you want to use for new_password in the preceding example. MySQL cannot tell you what the original password was, so you'll need to pick a new one.

  • Tell the server to use the older password hashing algorithm by default:

    1. Start mysqld with the old_passwords system variable set to 1.

    2. Assign an old-format password to each account that has had its password updated to the longer 4.1 format. You can identify these accounts with the following query:

      mysql> SELECT Host, User, Password FROM mysql.user
          -> WHERE LENGTH(Password) > 16;

      For each account record displayed by the query, use the Host and User values and assign a password using one of the methods described previously.

The Client does not support authentication protocol error also can occur if multiple versions of MySQL are installed but client programs are dynamically linked and link to an older library. Make sure that clients use the most recent library version with which they are compatible. The procedure to do this depends on your system.


The PHP mysql extension does not support the authentication protocol in MySQL 4.1.1 and higher. This is true regardless of the PHP version being used. If you wish to use the mysql extension with MySQL 4.1 or higher, you may need to follow one of the options discussed above for configuring MySQL to work with old clients. The mysqli extension (stands for "MySQL, Improved"; added in PHP 5) is compatible with the improved password hashing employed in MySQL 4.1 and higher, and no special configuration of MySQL need be done to use this MySQL client library. For more information about the mysqli extension, see

For additional background on password hashing and authentication, see Section, “Password Hashing in MySQL”.