Saving in legacy formats involves creating files compatible with outdated software or operating systems. Older OS versions, like Windows XP or macOS Snow Leopard, often lack native support for modern file standards such as DOCX or PNG. Therefore, users need to actively select older format options like DOC or GIF during the "Save As" process in compatible software applications that provide this backward compatibility feature.

A common practice involves saving documents in DOC format using old Word versions for use in proprietary systems at manufacturing plants. Preservation projects archive images or recordings in TIFF or WAV formats when accessing original, decades-old software on vintage hardware requires exact matches. Tools like LibreOffice and GIMP often include specific legacy export options to facilitate this.

This process enables essential access to obsolete systems but has significant limitations. Legacy formats frequently lack modern security features or efficient compression, increasing risks of vulnerabilities and corruption. Support loss can lock away data permanently. Emulation and conversion tools offer potential future solutions, though ethical preservation efforts currently depend heavily on maintaining functioning old software and carefully executed "Save As" selections.