Jun 12, 2022 | Email Conversion

How to Fix Microsoft SQL Server Error 18456?

By Deepak Singh Bisht

In this post, we will learn about SQL Server error 18456 and the reasons for this error. We will also learn how to fix Microsoft SQL Server Login Failed error 18456. If you are also facing this problem and looking for a simple way to fix it, then this post will help you.

What is SQL Server error 18456?

SQL Server error 18456 is caused by authentication issues. Error 18456 is displayed if the server name you entered is correct, but the connection could not be granted due to one of several reasons. SQL Server error message 18456 does not provide much information because it is intended to hide details from unauthorized users. So that, one cannot enter SQL Server by guessing the information.

Causes of SQL server error 18456

Microsoft SQL Server uses two types of authentication. One is Windows Authentication, and the other is SQL Server Authentication. Together we call this mixed-mode authentication. This error occurs when mixed-mode authentication is enabled. This error can occur if

  1. You are trying to log in using Windows Authentication with a user that SQL Server does not recognize as a SQL User login.
  2. You are using SQL Server Authentication and the login or password is incorrect.
  3. Your password is expired.

How to fix SQL Server login failed error 18456?

Before proceeding with troubleshooting, verify that your credentials are correct. If everything is fine, then you can use the following method to solve this issue. To perform this solution, follow the steps below.

  1. Open SQL Server Management Studio (SSMS)
  2. Select Windows Authentication from the Authentication drop-down
  3. Click on the connect button
  4. Right-click on the instance and go to the properties
  5. From the server properties window, select the Security option
  6. Choose SQL Server and Windows Authentication mode option and click on the OK button.
  7. A message will pop up "Some of your configuration changes will not take effect until SQL Server is restarted."
  8. Click on the OK button.
  9. Right-click on the instance and choose restart
  10. Click on the Yes button.
  11. Disconnect and reconnect again
  12. Select SQL Server authentication from the Authentication drop-down
  13. Enter login and password details and click on the connect button


The above method will help you to fix Microsoft SQL Server Login Failed error 18456. But before executing this solution, verify that your credentials are correct and your password has not expired.

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