What is BAK?

BAK (.bak) files are backup copies of original files. When software modifies a file, it often creates a .bak copy first to enable recovery if something goes wrong. BAK files contain identical content to the original file at the time of backup. To use a BAK file, rename it back to the original extension (e.g., document.bak → document.docx).

Common sources include text editors (Notepad++, Sublime), CAD software (AutoCAD), databases (SQL Server), configuration files, and any software offering automatic backup functionality.

Did you know? BAK files have saved countless projects from accidental data loss!

History

The .bak extension is a convention dating back to early computing when file recovery tools were limited. Software developers adopted it as a simple way to indicate backup copies.

Key Milestones

  • 1970s-80s: Early text editors create .bak backups
  • 1990s: Windows applications standardize on .bak
  • 2000s: Database systems use .bak for SQL backups
  • 2010s: CAD and design software adopt format
  • Present: Universal backup indicator

Key Features

Core Capabilities

  • Exact Copy: Identical to original file
  • Easy Recovery: Rename to restore
  • Automatic Creation: Software-generated
  • Version History: Preserve older versions
  • No Special Format: Original file structure
  • Safety Net: Recover from mistakes

Common Use Cases

Databases

SQL Server .bak backups

CAD Files

AutoCAD drawing backups

Text Editors

Source code backups

Config Files

Settings preservation

Advantages

  • Simple recovery process
  • No special software required
  • Preserves original content
  • Automatic generation
  • Universal convention
  • Easy to identify backups

Disadvantages

  • Takes up storage space
  • Can clutter directories
  • No compression (usually)
  • Single version only (typically)
  • May contain sensitive data

Technical Information

Format Specifications

Specification Details
File Extension .bak
MIME Type application/octet-stream
Format Type Generic backup
Content Copy of original file
Structure Same as original
Recovery Rename to original extension

Common Tools

  • Creation: Text editors, databases, CAD software
  • Recovery: Rename file extension
  • Management: File explorers, backup tools