The SQL error 18456 can occur due to several reasons. This tutorial shows how to remove this login failed error and also provides alternative solution.

2. • SQL Server Error 18456 – An Overview
• Event Properties Of Error 18456
• Causes of SQL Server Error 18456
• How to Resolve Error 18456 ?
• Conclusion

3. SQL Server Error 18456 – An Overview
The SQL Error 18456 “Login Failed” occurs due to various reasons. One of
the main reason is, The connection is failed to access to the Server after
entering the correct Server name .
The below error message displays when the SQL Error 18456 occurs.

4. Event Properties Of Error 18456
The Login Failed Error 18456 not provide the much detail about occurrence of this
error. The information is hide to prevent from unauthorized user access.
Although, you can view more information regarding to this error by checking Event
Viewer.

5. Causes of SQL Server Error 18456
 Mixed mode is enabled and you may trying to connect with Windows
authentication mode.
 The Login or Password is incorrect when you are using SQL Server
Authentication.
 May the SA password you are using has been expired.

6. How to Resolve Error 18456 ?
 For Windows 7, Use “Run as Admin” to open SQL Server and check if the problem
is solved. (Use also for Windows Vista)
 Check, may the Active Directory Windows account is not corresponding to SQL
login

7.  Use SQL SA password, if you are connecting through SQL Server
authentication.
 Check for SA Expiration by clicking on:
Logins > user > properties

8.  Under the General tab, check, if Enforce password expiration is enabled or
disabled

9. Next, Go to Status tab and Check , if “Login is locked out” option is enabled or
disabled.

10.  The SQL error 18456 can also occur, if Windows or Mix Mode Authentication is
disabled by itself on the database instance.
 To check this, Right click on database instance and click on Properties.

11.  Now, under the Security tab check the Server authentication mode.

12.  You need to Restart the SQL Server Service either if you choose “Windows
Authentication mode” or “SQL Server and Windows Authentication”
 To restart the service right click on database instance and click on Restart.

13. Conclusion
SQL Server error 18456 may arise from several reasons. Mostly the error occurs, if
user forgets its SA password or if user had tried Windows login name with SQL
Authentication. The above mentioned steps help you to fix SQL Error 18456. But, if
you still facing this error, the SQL Password Recovery software is more preferable
to troubleshoot this “Login Failed” error.
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