What is the DSN file format?
.dsn files are used by various database programs to connect to databases. A .dsn file stores information necessary for establishing a remote connection with a database, including server address, driver name, user ID, and database name - though credentials stored in the file remain in clear text, which is a security consideration.
Data in text format
Data in .dsn files is saved in plain-text INI-style format, organized under an [ODBC] section header with key=value pairs such as DRIVER=, SERVER=, and DATABASE=. A typical .dsn file is under 1 KB. However, some database applications instead of .dsn files use entries in the Windows registry (System or User DSNs) - only File DSNs exist on disk as .dsn files.
.dsn files as a means of connecting to a database
ODBC (Open Database Connectivity) application drivers use .dsn files for establishing connections to databases - for example, Microsoft Access (.accdb / .mdb) or Microsoft SQL Server. The .dsn file itself contains no table data; it is a small connection pointer that tells the ODBC driver how to locate and authenticate to the target database. Beyond Windows, macOS (via iODBC) and Linux (via unixODBC) can also read .dsn files. A .udl file serves a similar purpose for OLE DB connections.
Security & safety
RISK: MEDIUMA .dsn is plain text and contains no executable code, so opening it cannot run anything. The real risk is confidentiality, not malware: a File DSN stores connection details in clear text - server name, database, login, and depending on the driver sometimes a password - so treat .dsn files like credentials. Don't email them around, don't commit them to public repos, and remove or mask passwords before sharing. If you received an unexpected .dsn, inspect it in a text editor before using it to see exactly what server it points at.
Format details
in a nutshellFULL NAMEODBC Data Source Name Fileaka File DSN, ODBC data source file
DEVELOPERMicrosoft (ODBC); part of the Open Database Connectivity standardsince Microsoft ODBC (early 1990s); File DSN since ODBC 3.0 (1996)
CATEGORYDatabase Files
MIME TYPEtext/plain
TYPEPlain-text INI-style connection configuration file
STANDARDOpen · royalty-free
This extension is also used by…
- OrCAD / Allegro PCB schematic design (.dsn) - Cadence OrCAD Capture design file (and Specctra/Allegro routing .dsn); an electronics CAD design, not an ODBC config.
- Design Compiler / EDA design files - Some electronic-design-automation tools use .dsn for circuit/board design data.
Programs that open DSN files
Windows4 apps
Microsoft Excel
Paid Data > Get Data > From Other Sources > From ODBC (or browse to the .dsn) to pull database data into a sheet. 
Microsoft Access
Paid Use the .dsn to link/import external tables (External Data > ODBC Database > File data source). 
ODBC Data Source Administrator (odbcad32.exe)
Built-in Run odbcad32.exe (Control Panel > Administrative Tools > ODBC Data Sources) > File DSN tab to create, test, edit or remove .dsn files.
Notepad / any text editor
Built-in Right-click > Open with > Notepad to read or edit the plain-text [ODBC] connection settings directly. 
macOS2 apps
iODBC Administrator
Open-source Use iODBC's administrator to create/edit File DSNs on macOS; or edit the text file directly. (Apple's old ODBC Administrator was dropped from modern macOS.)
TextEdit / any text editor
Built-in Open the .dsn as plain text to read or edit the connection keys. 
Linux1 app
unixODBC
Open-source Manage ODBC data sources with unixODBC (odbcinst / ODBCConfig); inspect or edit the .dsn as a text file. Technical details
deep spec| Format type | Plain-text INI-style connection configuration file |
| MIME type | text/plain |
| File encoding | ASCII / ANSI; no Unicode requirement |
| Typical file size | Under 1 KB - a few lines of key=value pairs |
| File structure | INI file with an [ODBC] section listing DRIVER=, SERVER=, DATABASE=, UID= and driver-specific keys |
| Binary signature | None - plain text; typically begins with the [ODBC] INI section header at offset 0 |
| Encryption | None - credentials stored in clear text (security risk if file is shared or left unprotected) |
| Platform support | Windows (native ODBC), macOS (iODBC, unixODBC), Linux (unixODBC) |
| Data content | Connection metadata only - no table data, rows, or schema |
| DSN storage types | File DSN (.dsn on disk), System DSN (Windows registry HKLM), User DSN (Windows registry HKCU) - only File DSN produces a .dsn file |
| Common connection keys | DRIVER, SERVER, DATABASE, UID, PWD, DBQ (for Access path), PORT - plus driver-specific keys |
| Managed by | ODBC Data Source Administrator (odbcad32.exe) on Windows, iODBC Administrator on macOS, or any plain-text editor |
| Common alternatives | UDL files (OLE DB), DSN-less connection strings embedded in application config |
| Released | Microsoft ODBC (early 1990s); File DSN since ODBC 3.0 (1996) |
| Latest version | N/A - tied to the ODBC driver/spec, not separately versioned |
| Open standard | Yes · royalty-free |
| Specification | learn.microsoft.com |
DSN conversions
Possible
.DSN .UDLGUIDE
Yes -- open the .dsn in Notepad, read the DRIVER/SERVER/DATABASE values, then build an equivalent .udl…
How to convert
.DSN .TXTGUIDE
Yes -- a DSN file is already plain text, so rename a copy or save it from any text editor.
How to convert
.DSN .PDFGUIDE
Yes - open the DSN in Notepad (or any text editor) and print to PDF. No dedicated converter needed.
How to convert
Community Q&A
asked by users
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Frequently asked questions
What is a DSN file?
It's an ODBC File Data Source Name - a tiny plain-text file that tells Windows (or another ODBC host) how to connect to a database: which driver, server, database and user. It contains no actual data, just connection settings.
How do I open a DSN file?
Open it in any text editor (Notepad/TextEdit) to read the settings, or manage it with the Windows ODBC Data Source Administrator (odbcad32.exe) on the File DSN tab. To use it, you also need the matching ODBC driver and access to the database it points to.
Does a DSN file contain my data?
No. A .dsn holds only connection settings (driver, server, database, login). The actual tables live in the database it points to - the .dsn is just a pointer.
What's the difference between File, System and User DSN?
System and User DSNs are stored in the Windows registry (System = all users, User = your account). A File DSN is the only one saved as a .dsn file on disk, so it can be copied or put on a network share to be shared.
Is it safe to share a DSN file?
Be careful - File DSNs store connection details in clear text and can include a username (and, with some drivers, a password). Treat them like credentials; remove sensitive fields before sharing.
Why does my .dsn open in a circuit/CAD program?
The .dsn extension is also used by OrCAD/Allegro electronics design tools for schematic and routing files. If your .dsn came from an EDA tool it's a circuit design, not an ODBC connection - open it in the CAD software, not a text editor.
References
1Microsoft Learn - Connecting with a File Data Source (DSN)learn.microsoft.com
2Microsoft Learn - ODBC Data Source Administratorlearn.microsoft.com
