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Applies to:SQL Server

Microsoft SQL Server Express LocalDB is a feature of SQL Server Express targeted to developers. It's available on SQL Server Express edition with Advanced Services. In SQL Server 2025 (17.x) and later versions, it's available on SQL Server Express edition.

LocalDB installation copies a minimal set of files necessary to start the SQL Server Database Engine. Once LocalDB is installed, you can initiate a connection using a special connection string. When you connect, the necessary SQL Server infrastructure is automatically created and started, enabling the application to use the database without complex configuration tasks. Developer Tools can provide developers with a SQL Server Database Engine that lets them write and test Transact-SQL code without having to manage a full server instance of SQL Server.

Installation media

LocalDB is a feature you select during SQL Server Express installation, and is available when you download the media. If you download the media, either chooseExpress Advanced or theLocalDB package.

Customers using Visual Studio 2019 and Visual Studio 2022 should install SQL Server 2019 Express edition.

The LocalDB installerSqlLocalDB.msi is available in the installation media for all editions except for Express Core. It's located in the<installation_media_root>\<LCID>_ENU_LP\x64\Setup\x64 folder. LCID is a locale identifier or language code. For example, an LCID value of 1033 refers to theen-US locale.

Alternatively, you can install LocalDB through theVisual Studio Installer, as part of theData Storage and Processing workload, theASP.NET and web development workload, or as an individual component.

Install LocalDB

Install LocalDB through the installation wizard or by using theSqlLocalDB.msi program. LocalDB is an option when installing SQL Server Express LocalDB.

Select LocalDB on theFeature Selection/Shared Features page during installation. There can be only one installation of the LocalDB binary files for each major SQL Server Database Engine version. Multiple Database Engine processes can be started, and all use the same binaries. An instance of the SQL Server Database Engine started as the LocalDB has the same limitations as SQL Server Express.

An instance of SQL Server Express LocalDB is managed by using theSqlLocalDB.exe utility. SQL Server Express LocalDB should be used in place of the SQL Server Express user instance feature, which was deprecated.

Description

The LocalDB setup program uses theSqlLocalDB.msi program to install the necessary files on the computer. Once installed, LocalDB is an instance of SQL Server Express that can create and open SQL Server databases. The system database files for the database are stored in the localAppData path, which is normally hidden. For example,C:\Users\<user>\AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\LocalDBApp1\. User database files are stored where the user designates, typically somewhere in theC:\Users\<user>\Documents\ folder.

For more information about including LocalDB in an application, see Visual StudioLocal Data Overview,Create a database and add tables in Visual Studio.

For more information about the LocalDB API, seeSQL Server Express LocalDB reference.

TheSqlLocalDB utility can create new instances of LocalDB, start and stop an instance of LocalDB, and includes options to help you manage LocalDB. For more information about theSqlLocalDB utility, seeSqlLocalDB utility.

The instance collation for LocalDB is set toSQL_Latin1_General_CP1_CI_AS and can't be changed. Database-level, column-level, and expression-level collations are supported normally. Contained databases follow the metadata andtempdb collations rules defined byContained database collations.

Restrictions

LocalDB can't be managed remotely via SQL Server Management Studio.
LocalDB can't be a merge replication subscriber.
LocalDB doesn't support FILESTREAM.
LocalDB only allows local queues for Service Broker.
An instance of LocalDB owned by the built-in accounts such asNT AUTHORITY\SYSTEM can have manageability issues due to Windows file system redirection. Instead use a normal Windows account as the owner.

Automatic and named instances

LocalDB supports two kinds of instances: automatic instances, and named instances. Different users of a computer can have instances with the same name. Each instance runs as the respective user in its own process.

Automatic instances

Automatic instances of LocalDB are public. They're created and managed automatically for the user and can be used by any application. One automatic instance of LocalDB exists for every version of LocalDB installed on the user's computer. Automatic instances of LocalDB provide seamless instance management. There's no need to create the instance; it just works. This feature allows for easy application installation and migration to a different computer. If the target machine has the specified version of LocalDB installed, the automatic instance of LocalDB for that version is available on the target machine as well. Automatic instances of LocalDB have a special pattern for the instance name that belongs to a reserved namespace. Automatic instances prevent name conflicts with named instances of LocalDB. The name for the automatic instance isMSSQLLocalDB.

Named instances

Named instances of LocalDB are private. They're owned by a single application that is responsible for creating and managing the instance. Named instances provide isolation from other instances and can improve performance by reducing resource contention with other database users. You must create named instances explicitly through the LocalDB management API, or implicitly via theapp.config file for a managed application (although managed application might also use the API, if desired). Each named instance of LocalDB has an associated LocalDB version that points to the respective set of LocalDB binaries. The instance name of a LocalDB issysname data type and can have up to 128 characters. (This instance name differs from regular named instances of SQL Server, which limits names to regular NetBIOS names of 15 ASCII characters.) The name of an instance of LocalDB can contain any Unicode characters that are legal within a filename. A named instance that uses an automatic instance name becomes an automatic instance.

Shared instances of LocalDB

To support scenarios where multiple users of the computer need to connect to a single instance of LocalDB, LocalDB supports instance sharing. An instance owner can choose to allow the other users on the computer to connect the instance. Both automatic and named instances of LocalDB can be shared. To share an instance of LocalDB, a user selects a shared name (alias) for it. Because the shared name is visible to all users of the computer, this shared name must be unique on the computer. The shared name for an instance of LocalDB has the same format as the named instance of LocalDB.

Only an administrator on the computer can create a shared instance of LocalDB. A shared instance of LocalDB can be unshared by an administrator or by the owner of the shared instance of LocalDB. To share and unshared an instance of LocalDB, use theLocalDBShareInstance andLocalDBUnShareInstance methods of the LocalDB API, or the share and unshared options of theSqlLocalDB utility.

Start LocalDB and connect to LocalDB

This section describes how to connect to an automatic instance, a named instance, or a shared instance.

Connect to the automatic instance

The easiest way to use LocalDB is to connect to the automatic instance owned by the current user by using the connection stringServer=(localdb)\MSSQLLocalDB;Integrated Security=true. To connect to a specific database by using the file name, connect using a connection string similar toServer=(LocalDB)\MSSQLLocalDB;Integrated Security=true;AttachDbFileName=D:\Data\MyDB1.mdf.

Note

The first time a user on a computer tries to connect to LocalDB, the automatic instance must be both created and started. The extra time for the instance to be created can cause the connection attempt to fail with a timeout message. When this happens, wait a few seconds to let the creation process complete, and then connect again.

Create and connect to a named instance

In addition to the automatic instance, LocalDB also supports named instances. Use theSqlLocalDB.exe program to create, start, and stop a named instance of LocalDB. For more information aboutSqlLocalDB.exe, seeSqlLocalDB utility.

REM Create an instance of LocalDB"C:\Program Files\Microsoft SQL Server\160\Tools\Binn\SqlLocalDB.exe" create LocalDBApp1REM Start the instance of LocalDB"C:\Program Files\Microsoft SQL Server\160\Tools\Binn\SqlLocalDB.exe" start LocalDBApp1REM Gather information about the instance of LocalDB"C:\Program Files\Microsoft SQL Server\160\Tools\Binn\SqlLocalDB.exe" info LocalDBApp1

The last line in the previous code sample, returns information similar to the following table.

Category	Value
Name	`LocalDBApp1`
Version	`<Current version>`
Shared name	`""`
Owner	`<Your Windows user>`
Auto create	`No`
State	`Running`
Last start time	`<Date and time>`
Instance pipe name	`np:\\.\pipe\LOCALDB#F365A78E\tsql\query`

Note

If your application uses a version of .NET Framework before 4.0.2, you must connect directly to the named pipe of the LocalDB. The Instance pipe name value is the named pipe that the instance of LocalDB is listening on. The portion of the Instance pipe name afterLOCALDB# will change each time the instance of LocalDB is started. To connect to the instance of LocalDB by using SQL Server Management Studio, type the instance pipe name in theServer name box of theConnect to Database Engine dialog box. From your custom program you can establish connection to the instance of LocalDB using a connection string similar toSqlConnection conn = new SqlConnection(@"Server=np:\\.\pipe\LOCALDB#F365A78E\tsql\query");

Connect to a shared instance of LocalDB

To connect to a shared instance of LocalDB, add\.\ (backslash + dot + backslash) to the connection string to reference the namespace reserved for shared instances. For example, to connect to a shared instance of LocalDB namedAppData, use a connection string such as(localdb)\.\AppData as part of the connection string. A user connecting to a shared instance of LocalDB that they don't own must have a Windows Authentication or SQL Server Authentication login.

Troubleshoot

For information about troubleshooting LocalDB, seeKnown SQL Server 2012 setup and migration issues.

Permissions

An instance of SQL Server Express LocalDB is an instance created by a user for their use. Any user on the computer can create a database using an instance of LocalDB, store files under their user profile, and run the process under their credentials. By default, access to the instance of LocalDB is limited to its owner. The data contained in the LocalDB is protected by file system access to the database files. If user database files are stored in a shared location, the database can be opened by anyone with file system access to that location, by using an instance of LocalDB that they own. If the database files are in a protected location, such as the users data folder, only that user, and any administrators with access to that folder, can open the database. The LocalDB files can only be opened by one instance of LocalDB at a time.

LocalDB always runs under the user's security context. LocalDB never runs with credentials from the local Administrator's group. This means that all database files used by a LocalDB instance must be accessible using the owning user's Windows account, without considering membership in the local Administrators group.