Digital files don't decay like prints, but they fail in their own ways: media wear out, formats lose support, and hardware to read them disappears. Preservation is an ongoing practice.

Format Choices

Safe for decades:

  • JPEG — the most universally supported image format in existence. Lossy, but its ubiquity is itself a preservation feature.
  • TIFF — the standard archival raster format: lossless, widely supported, and stable for decades.
  • PNG — open, lossless, universally supported.

Riskier:

  • Proprietary camera RAW (CR3, NEF, ARW and dozens of others) — each is a manufacturer-specific format tied to specific software. Support for discontinued formats does erode, and there are already RAW formats from the 2000s that are awkward to open today.
  • DNG is the mitigation: an openly documented RAW container. Converting proprietary RAW to DNG for archival purposes is a reasonable hedge, though it's a trade-off some photographers dislike.
  • Newer formats (AVIF, JPEG XL, HEIC) — excellent technically, but shorter track records. Fine as derivatives; think twice before making one your only archival copy.

The practical policy: archive the original capture file *plus* a widely-supported derivative. A RAW plus a high-quality JPEG covers both the "best quality" and the "will definitely still open" requirements.

Media and Their Lifespans

  • Hard drives — 3–5 years of reliable service; they fail suddenly. Fine as one copy, never as the only one.
  • SSDs — fast and robust in use, but can lose data when left unpowered for years. Not an archival medium.
  • Optical discs — archival-grade discs claim long life, but drives to read them are disappearing.
  • Tape — genuinely long-lived, used by institutions, impractical for individuals.
  • Cloud — durability is excellent while you keep paying and the provider exists. Both are assumptions.

The honest conclusion: there is no set-and-forget medium. Every option requires periodic migration.

Bit Rot and Verification

Files can degrade silently — a flipped bit from media wear or a bad transfer, producing a corrupted image that opens fine until you look closely.

Protect against it:

  • Store checksums (hashes) alongside your archive, and verify periodically. Some filesystems do this automatically and can self-heal from a redundant copy.
  • Verify after every migration, not just at rest.
  • Keep multiple copies so a corrupted file can be replaced from a good one. This is the practical reason redundancy matters more than any single medium's reliability.

The Migration Habit

This is what actually preserves data over decades:

  • Every 3–5 years, move your archive to new media.
  • Re-verify checksums as part of the move.
  • Review format support at the same time; convert anything whose format is fading while software that reads it still exists.
  • Write down what you did, so the next person — including future you — understands the structure.

Don't Forget the Context

An archive of unlabelled files loses much of its value. Preserve:

  • Metadata — keep IPTC/XMP captions, dates, names and locations embedded in the files, not only in a catalogue database that may not outlive its software.
  • A plain-text index describing folders, projects and people. Plain text will open in fifty years; a proprietary catalogue may not.
  • Prints of the most important images. A physical print requires no format support at all, and remains the single most robust long-term backup for a handful of irreplaceable photographs.