Long-term file formats


This Guideline identifies file formats that the National Archives has reasonable confidence will continue to be accessible over time. The Guideline is intended to have the following uses:

  • restrict the number and types of file formats transferred by government agencies and personal records donors to those formats the National Archives is confident can be preserved and made accessible over time;
  • provide a resource to help government agencies make risk-based decisions about file format selection for activities like digitisation projects or other digital projects;
  • indicate preferred formats for digitisation projects undertaken by the National Archives, both internally and outsourced to a third party service provider;
  • provide information about the National Archives' approach to digital preservation for digital records that have been transferred into our custody.

The Guidelines are not intended to be exhaustive, but to identify the common types of formats the National Archives expects to receive from agencies and provide an indication of their long-term sustainability.
Agencies can contact the National Archives if they have identified other file formats they would like investigated and added to the table.

Characteristics of preservation formats

The National Archives distinguishes between 'preferred', 'acceptable' and 'at risk' preservation formats. 'Preferred' preservation formats are formats that the National Archives has determined are a very low risk of becoming obsolete in the long term. The National Archives normalises 'at risk' formats into a 'preferred' preservation format.

'Acceptable' preservation formats are formats that the National Archives has determined are a low risk of becoming obsolete in the long term. Records in 'acceptable' formats are not normalised but are stored as they are and are monitored over time to confirm their continued accessibility.

'At-risk' formats are those the National Archives has determined are at significant risk of becoming inaccessible. The National Archives will normalise these digital records into 'preferred' preservation formats. If there is no 'preferred' preservation format for the material it will be retained in its native format until a preferred format is identified, at which time the format will be normalised to it.

Transfer requirements

When transferring digital records to the National Archives, the transferring agency will identify the category and format of the records in the transfer documentation. While the National Archives always prefers to receive a preferred file format over an acceptable file format, there may be sound business reasons why the agency has selected an acceptable file format.

The transferring agency will need to take further actions to ensure that digital records are acceptable for transfer:

  • Provide metadata in a digital file as set out in the National Archives transfer requirements
  • Deactivate any file level encryption
  • Deactivate any digital rights management technologies
  • Provide Representation Information, which is information or documentation required to access the record or to provide additional technical information, eg data dictionaries, manuals etc.

Note that this Guideline is not a procedure for transferring digital records to the National Archives. Transfer procedures can be discussed with the National Archives' officer responsible for the transfer.

Table of file formats