1. Distinguish the four file types
Museums that preserve time-based media, such as the Tate, always separate:
- The master: the highest quality and most complete version of the work, from which all others are derived. It is neither exhibited nor distributed; it is archived.
- The exhibition copy: the version utilised in the gallery or on a screen, prepared for specific equipment.
- The derivatives: thumbnails, or versions intended for web or press use.
- The documentation: instructions, technical specifications, installation photographs, interviews and correspondence.
Should an exhibition copy become corrupted, another is generated from the master. If the master is lost, the approved reference from which copies should be generated is lost, even if partial sources or derivatives remain.
2. What constitutes the master
This depends upon the work. At a minimum:
- The files of the work in their highest quality.
- The working files, if the ability to recreate or migrate the work depends upon them: editing projects, layers and source code.
- The dependencies: typefaces, libraries, software or external resources without which the work cannot function.
- The presentation parameters: resolution, aspect ratio, audio, duration and looping status.
For software-based works, the Guggenheim recommends also retaining a disk image of the equipment on which it operates and an inventory of all its components.
3. Select durable formats
The United States Library of Congress publishes a guide to recommended formats annually. Their general preferences are:
- Still image: Uncompressed TIFF or lossless compression, or lossless JPEG 2000.
- Video: Lossless formats or frame-by-frame compression. ProRes or MP4 are acceptable in certain instances, but they are not the primary choice for a master.
- Audio: Uncompressed WAVE or Broadcast WAVE.
- Web: WARC format captures, plus the files and dependencies.
This guide is intended for published content and does not replace a preservation policy: if the work was created in a proprietary format, retain the original as well, as conversion may alter it.
4. Create multiple copies and verify them
The digital preservation guidelines of the National Digital Stewardship Alliance require multiple copies in distinct locations, with an inventory of the contents of each. A standard rule of thumb is to maintain three copies, on at least two different media, with one stored off-site.
To determine if a copy remains intact, checksums are utilised: a code calculated from the file that changes if the file changes, even by a single bit. Calculate the sum when saving the master, store it separately and recalculate it each time you copy or move the files and, at a minimum, once a year.
5. Name and version using a fixed criterion
There is no single standard for naming the files of a digital work. The essential requirement is that the name indicates what the file is and which version it represents without requiring the file to be opened. A simple schema:
surname_short-title_year_type_v01_date
For example: esteban_umbral_2026_master_v02_20261017.tif or esteban_umbral_2026_exhibicion-1080p_v02_20261017.mp4.
And a few rules:
- Never overwrite a master: every change generates a new version.
- Maintain a change log: a text file detailing each version, its date, what was changed and why.
- Relate each copy to its master: ensure the exhibition copy indicates which version of the master it is derived from.
Checklist
- The master is identified and separated from the copies.
- It includes the necessary working files and dependencies.
- It is in recommended formats, and also in the original format if it was proprietary.
- There are at least three copies, with one off-site.
- Each copy has its checksum, verified at least once a year.
- The files follow a naming schema and there is a change log.
- The technical specification indicates the location of each file.
If you intend to sell or transfer the work, the master serves as the basis for the certificate.
Further reading
- Tate, Time-based Media Conservation.
- Guggenheim, The Conserving Computer-Based Art Initiative.
- Matters in Media Art.
- Library of Congress, Recommended Formats Statement.
- NDSA, Levels of Digital Preservation.
About the open conversation
This guide remains open to corrections and documented cases. Should you detect an error or utilise a procedure that allows for the refinement of any of these steps, you may write to me.