.bak

How to Open BAK File: Find Out What It Is and Restore It

A BAK file is a backup copy that some program made automatically, so the way to open it depends on which program: a SQL Server database backup is restored in SQL Server, an AutoCAD .bak is renamed to .dwg, and "report.docx.bak" just needs the .bak removed. To open BAK files you're unsure about, drop one into the free identifier below. It reads the content, names the real format and gives you a correctly named copy.

Guide by the File-Extension.com team — see our methods and tool limitations. Published · Updated .

Category: Backup copy Developer: Various programs Format: Depends on the program Most common: SQL Server, AutoCAD

Choose what you need

Find out what my BAK file is Restore a SQL Server .bak Open an AutoCAD .bak Restore "name.ext.bak" files Can I delete BAK files?

Open BAK File Online: Identify & Restore It (Free)

Drop a .bak below, any size. The identifier reads the first bytes to tell SQL Server backups, AutoCAD drawings, Word/Excel files, SQLite and PostgreSQL databases, SQL dumps, browser bookmark backups, archives and text files apart. It then shows step-by-step instructions, a preview for text files and a copy with the right extension.

Good to know: the copy is the same data with a new name; nothing is converted, and your original stays untouched.

🔒 Nothing is uploaded — your file never leaves this device

On this page

  1. Open BAK file online (free identifier)
  2. What is a BAK file?
  3. How to open a BAK file: quick answer
  4. Restore a SQL Server BAK
  5. Open an AutoCAD BAK
  6. Other BAK files
  7. Mac and phones
  8. Can I delete BAK files?
  9. Related file extensions
  10. Sources
  11. FAQ

What is a BAK file?

A BAK file is a backup copy of another file, created by a program before it overwrites or changes the original. ".bak" is a naming habit, not a format: the bytes inside are whatever the original program uses. That's why no single "BAK opener" exists, and why the first step is always finding out which program made it.

Where it came fromTypical nameWhat's insideHow to open it
Microsoft SQL ServerSalesDB_full.bakDatabase backup (Microsoft Tape Format)Restore in SQL Server
AutoCAD and other DWG appsfloorplan.bak next to floorplan.dwgThe drawing before the last saveRename to .dwg
Text editors, installers, appssettings.ini.bak, hosts.bakEarlier copy of that fileRemove ".bak"
Chrome / EdgeBookmarks.bakBookmarks (JSON)Swap with Bookmarks
Database toolssite.sql.bak, db.bakSQL dump, SQLite or PostgreSQL backupMatching database tool
How to figure out what a BAK file is Start with the file name: if it is name.ext.bak, remove .bak. Otherwise look at the folder for a file with the same name, such as a DWG drawing. If neither helps, check the content with the identifier, which reads the file signature. 1. Namename.ext.bak? 2. Foldersame-name file? 3. Contentfile signature "TAPE" → SQL Server backup → restore in SSMS "AC1032" → AutoCAD drawing → rename to .dwg "PK" → Office file or ZIP → rename to .docx/.xlsx/.zip "SQLite format 3" → SQLite database
Illustration: three clues identify almost any BAK file. The identifier above checks the third one for you.

How to open a BAK file: quick answer

  1. Make a copy of the .bak first, so you can't damage the only backup.
  2. Read the name: if it ends in .ext.bak (for example budget.xlsx.bak), remove ".bak" from the copy and open it normally.
  3. Check the folder: a .bak next to a .dwg with the same name is an AutoCAD backup.
  4. Still unsure? Drop it into the identifier; it tells you the real format and what to do.

Restore a SQL Server BAK file

SQL Server backups can't be opened like a document; you restore them into a SQL Server instance. Free options: SQL Server Express (in SQL Server 2025 it supports databases up to 50 GB) or Developer edition, plus SQL Server Management Studio (SSMS).

  1. In SSMS, connect to your server, right-click Databases and choose Restore Database…
  2. Under Source, select Device, click …, then Add and pick the .bak file.
  3. Check the database name under Destination and, on the Files page, where the data and log files will be created.
  4. Click OK. To overwrite an existing database, tick Overwrite the existing database (WITH REPLACE) on the Options page.
Illustration: restoring a .bak from a file ("Device") in SQL Server Management Studio.

With T-SQL, look inside first, then restore:

RESTORE FILELISTONLY FROM DISK = 'C:\Backups\SalesDB_full.bak';

RESTORE DATABASE SalesDB FROM DISK = 'C:\Backups\SalesDB_full.bak'
WITH MOVE 'SalesDB' TO 'C:\Data\SalesDB.mdf',
     MOVE 'SalesDB_log' TO 'C:\Data\SalesDB_log.ldf';

Version rule: a backup restored to a newer SQL Server is upgraded automatically, but a backup made on a newer SQL Server can't be restored on an older one. If restore fails with a version error, install the same or a newer SQL Server.

Open an AutoCAD BAK file

By default AutoCAD creates drawing.bak in the same folder each time you save drawing.dwg. It's the previous version of the drawing. Autodesk's instruction is simply to rename the backup to a .dwg file:

  1. Copy floorplan.bak and rename the copy to floorplan-restored.dwg (turn on file extensions in File Explorer: View > Show > File name extensions).
  2. Open it in AutoCAD, AutoCAD LT or the free DWG TrueView.

The identifier also shows the drawing's format version (for example AC1032 = AutoCAD 2018 format). See our DWG guide for viewers. Autosave files (.sv$) are a separate mechanism and are renamed to .dwg the same way.

Other BAK files

  • name.ext.bak (e.g. config.ini.bak, index.php.bak): an earlier copy of name.ext. To restore it, rename the current file (keep it just in case) and remove ".bak" from the backup.
  • Chrome or Edge Bookmarks.bak: with the browser closed, rename the current Bookmarks file in your profile folder, rename Bookmarks.bak to Bookmarks, and reopen the browser.
  • SQL dumps (text starting with "-- MySQL dump" or "-- PostgreSQL database dump"): open in a text editor, import with mysql or psql.
  • SQLite databases: open with DB Browser for SQLite.
  • PostgreSQL custom dumps (start with "PGDMP"): restore with pg_restore.
  • Unknown binary: check which program uses that folder; its help usually names its backup files.

Renaming never changes the data. If the renamed copy doesn't open, rename it back; nothing is lost.

Open BAK files on Mac, iPhone or Android

The same rules apply: identify the file, then use a program for that format. On a Mac, rename the copy in Finder (select it, press Return, change the extension, choose "Use .dwg" or similar). SQL Server runs on Linux and in Docker, so Mac users usually restore SQL Server backups into a container or a Windows machine. On phones, the identifier on this page works in the browser, and text-based backups can be read in its preview.

Can I delete BAK files?

Usually yes, once you're sure the current file is fine: a .bak is only an older copy. Keep database backups (.bak from SQL Server) unless you have newer ones, because they may be your only way back after a failure. AutoCAD recreates its .bak on the next save; you can turn this off with the ISAVEBAK setting, but backups are cheap insurance.

Sources and technical references

Frequently asked questions

How do I open a BAK file?

First find out which program made it, because .bak is just a backup copy. Remove .bak from names like report.docx.bak, rename AutoCAD backups to .dwg, and restore SQL Server backups in SQL Server Management Studio. The free identifier on this page reads the file and tells you which case applies.

How do I open a SQL Server BAK file?

Install SQL Server (Express is free) and SQL Server Management Studio, right-click Databases, choose Restore Database, select Device, add the .bak file and click OK. With T-SQL, run RESTORE FILELISTONLY to see its files, then RESTORE DATABASE with MOVE options.

How do I open an AutoCAD BAK file?

Make a copy of the .bak, rename the copy's extension to .dwg and open it in AutoCAD, AutoCAD LT or the free DWG TrueView. It contains the drawing as it was before the last save, which makes it useful when the current DWG is damaged.

Can I convert a BAK file to Excel or PDF?

Only if the BAK already contains that kind of file. If the identifier says it's an Excel workbook or a PDF, just rename it. A SQL Server backup must be restored first; then you can export tables to Excel from SQL Server Management Studio.

Is it safe to delete BAK files?

Usually yes, if the current version of the file works, because a BAK is only an older copy. Keep SQL Server .bak files unless you have newer backups, since they may be the only way to recover a database. AutoCAD creates a new .bak each time you save.

Why can't I restore my SQL Server BAK file?

The most common reasons are a backup made on a newer SQL Server than yours, missing permissions on the folder, an incomplete copy of the file, or restoring over an existing database without the WITH REPLACE option. Microsoft's restore dialog and RESTORE FILELISTONLY help diagnose each.

Can I open a BAK file without SQL Server?

You can't read the tables of a SQL Server backup without restoring it into SQL Server, but you can use the free Express or Developer edition. Other BAK types, such as text, Office or SQLite backups, open with ordinary programs once renamed.

What program opens BAK files?

No single program: SQL Server opens SQL backups, AutoCAD or DWG TrueView opens drawing backups, Word or Excel open Office backups, DB Browser for SQLite opens SQLite backups and any text editor opens configuration backups. The identifier on this page tells you which one you need.

How do I open a BAK file on Mac?

Identify it first with the tool on this page. Rename text, Office or DWG backups in Finder and open them with the matching Mac app. SQL Server backups need SQL Server, which Mac users usually run in Docker or on a Windows machine.

What does file.ext.bak mean?

It's a backup of file.ext saved by an editor, installer or app before changing it. To restore it, keep a copy of the current file, then rename the backup by removing .bak at the end. The content is unchanged, so it opens like the original.

Last updated .