Category: Digital Preservation

Format Migration

Also known as: File Format Migration

Simply put

Format migration is the process of converting digital files from an obsolete or ageing file format into a more current, standardized one so that the content remains accessible over time. The information carried by the file is preserved, even though the underlying digital encoding changes. It is a common technique used to guard against the risk that older formats can no longer be opened or rendered.

Formal definition

Format migration is a preservation action involving the transformation of digital content from an ageing or obsolete file format into a modern or standardized target format, with the objective of preserving intellectual content and continued usability while the bitstream itself is not retained unchanged. It is distinct from storage media migration, which concerns the transfer of data between physical carriers or storage systems without necessarily altering the format. In archival terminology the term has historically been applied imprecisely and has at times been used to encompass media migration; current practice typically reserves it for format-level transformation. Because migration changes the encoding, practitioners generally weigh implications for authenticity, integrity, and the fidelity of the rendered content, and it should be considered one option among several digital preservation strategies rather than a universal solution.

Why it matters

Digital content depends on the continued availability of software and technical environments capable of interpreting a given file format. When a format ages or falls out of common use, organizations face the risk that files can no longer be opened or correctly rendered, even though the underlying bits may remain intact on storage. Format migration addresses this risk directly by converting content into a more current or standardized format, aiming to keep the intellectual content accessible over the long term. For records that must remain usable as evidence of activity for extended retention periods, the ability to render content reliably is often as important as retaining the file itself.

Because migration changes the encoding rather than preserving the original bitstream unchanged, it carries implications that recordkeeping and preservation professionals typically weigh carefully. Converting a file can affect the fidelity of the rendered content and raises questions about authenticity and integrity, since the migrated file is not a bit-for-bit copy of the original. Depending on organizational policy and the nature of the material, practitioners may need to document the migration action, verify that significant properties of the content have been retained, and consider whether the original should be kept alongside the migrated version. These considerations mean that migration is generally treated as one option among several digital preservation strategies rather than a guaranteed or universal solution.

Who it's relevant to

Digital preservation practitioners

Those responsible for keeping digital content accessible over time use format migration as one of several preservation actions. They typically evaluate when migration is appropriate, select suitable target formats, and assess trade-offs against alternative strategies, keeping in mind that migration is not a universal solution.

Records managers and archivists

Where records must remain usable across long retention periods, format obsolescence can threaten the ability to render and rely on those records. Records professionals are concerned with how migration affects authenticity, integrity, and fidelity, and with documenting migration actions so that the migrated content can still serve as reliable evidence of activity.

IT and storage administrators

Because format migration is often confused with storage media migration, administrators managing carriers, storage systems, and data transfers benefit from understanding the distinction. Moving data between systems without altering its format is a different activity from transforming the format itself, and the two may need to be planned and governed separately.

Information governance and compliance leads

Those setting policy for how digital information is retained and maintained may need to establish when and how migration is performed, what documentation is required, and how decisions balance continued usability against the risks that changing a file's encoding can pose to authenticity and integrity. Specific requirements often depend on jurisdiction, sector, and organizational policy.

Inside Format Migration

Source and target formats

The originating file or data format and the destination format into which content is converted. Format migration typically involves moving records from an obsolete, at-risk, or proprietary format to one considered more sustainable or better supported, though the choice depends on organizational policy and preservation objectives.

Significant properties

The characteristics of a record that should be preserved through migration so that its authenticity, reliability, integrity, and usability are maintained. These may include content, structure, appearance, and context, and identifying them is often a prerequisite to any responsible migration.

Conversion process

The technical transformation applied to move content from source to target format, which may be performed by tools, scripts, or specialized preservation systems. The process itself is distinct from the decision to migrate and from the validation that follows.

Validation and quality assurance

The checks performed after conversion to confirm that significant properties have been retained and that no material loss or corruption has occurred. Validation supports the ongoing integrity of the record as evidence rather than merely confirming that a file opens.

Provenance and audit documentation

Records of what was migrated, when, by whom, using which tools and settings, and what changes resulted. Such documentation is often important to demonstrating that a migrated record remains authentic and can be relied upon, though specific expectations vary by organization and jurisdiction.

Relationship to disposition

Format migration is a lifecycle activity typically associated with retention and continued access rather than disposition in the sense of destruction. It is one technique among several, sometimes contrasted with emulation, for keeping records usable over time.

Common questions

Answers to the questions practitioners most commonly ask about Format Migration.

Is format migration the same as making backup copies of records?

No. Backup copies typically reproduce records in their existing format to guard against loss or corruption, whereas format migration involves converting records from one file format to another, often because the original format is becoming obsolete or difficult to render. Backups are a continuity and recovery measure; migration is a preservation activity aimed at maintaining ongoing accessibility and usability. The two may be used together, but they serve different purposes and address different risks.

Does migrating a record to a new format always preserve it as an authoritative record?

Not necessarily. Migration changes the technical form in which a record is stored, and this can affect the properties that make something an authoritative record, particularly integrity and, in some cases, authenticity. Whether the migrated version remains a reliable record depends on how faithfully its content, structure, and relevant context are carried across, and on whether the migration process itself is documented and controlled. Depending on organizational policy and applicable requirements, uncontrolled or poorly documented migration may weaken the evidential value of the record.

How should a migration process be documented?

In many recordkeeping environments, migration is documented to preserve the integrity and usability of the affected records over time. Documentation often covers what was migrated, the source and target formats, the tools or methods used, when the migration occurred, and who authorized and carried it out. Capturing this information typically supports later verification that content and relevant context were retained, and helps demonstrate that the records remained under control throughout. The specific level of detail expected depends on organizational policy and, in some cases, applicable regulatory or standards-based expectations.

What should be checked after a migration to confirm it was successful?

Verification often focuses on confirming that the migrated records remain complete, accurate, and usable, and that their content and relevant structure and context have been carried across. Depending on organizational policy, this may involve comparing migrated records against their originals, checking that they render correctly, and confirming that associated metadata and links to related records are intact. The aim is generally to establish that the properties supporting the record's reliability and integrity have not been degraded by the conversion.

Which records should be prioritized for format migration?

Prioritization typically reflects a combination of factors, including how much the original format is at risk of obsolescence, the retention requirements applying to the records, and their ongoing value as evidence. Records with long or indefinite retention, or those held in formats that are becoming difficult to render, are often given greater attention. Because requirements and priorities depend on jurisdiction, sector, and organizational policy, prioritization is usually determined against the organization's own preservation objectives and risk assessment rather than a single fixed rule.

Should the original format be retained after migration?

This depends on organizational policy and any applicable requirements. In some cases the original is retained for a period so that the migrated version can be verified against it, or to preserve characteristics that the target format may not fully capture. In other cases, once migration is verified and documented, retaining the original may no longer be necessary. Any decision to dispose of the original should generally be made under the organization's disposition arrangements rather than treated as an automatic consequence of migration.

Common misconceptions

Format migration is the same as making a backup copy.

A backup typically reproduces content in its existing format to guard against loss, whereas format migration deliberately changes the format and therefore carries a risk of altering significant properties. The two serve different purposes and migration generally requires validation that a simple backup does not.

If a migrated file opens successfully, the migration was successful.

Openability alone does not confirm that the record's significant properties, integrity, or usability as evidence have been preserved. Migration can introduce subtle loss of content, structure, formatting, or context that only structured validation is likely to detect.

Migration permanently solves the problem of format obsolescence.

Migration typically addresses a specific obsolescence risk at a point in time, but target formats can themselves become at risk later. Maintaining usable records over the long term is often an ongoing activity that may require repeated migration or alternative strategies such as emulation, depending on organizational policy.

Best practices

Identify and document the significant properties of the records before migrating, so that success can be judged against explicit criteria for authenticity, reliability, integrity, and usability.

Select target formats with sustainability and continued support in mind, guided by organizational preservation policy rather than convenience alone.

Validate migrated records through structured quality assurance rather than relying on the fact that a file opens, and address any detected loss or corruption before treating the migration as complete.

Maintain provenance and audit documentation recording what was migrated, when, by whom, and with which tools and settings, to support the continued reliability of the record as evidence.

Retain the source records where appropriate until migration has been verified, and align any subsequent disposition of superseded copies with the applicable retention and disposition rules, which vary by jurisdiction and sector.

Treat format migration as a potentially recurring activity by monitoring the ongoing viability of target formats rather than assuming a single migration resolves obsolescence permanently.