Category: Digital Preservation

Emulation

Simply put

Emulation is the use of software to imitate the behavior of a different computer system or program, allowing older digital material to be accessed on newer equipment. In digital preservation, it enables files and software that depend on obsolete environments to continue functioning without altering the original content. It is one of several strategies used to keep digital records usable over time.

Formal definition

In the recordkeeping and digital preservation context, emulation is a preservation strategy in which software (an emulator) mimics the behavior of a legacy hardware or software environment so that digital objects can be rendered and accessed in something close to their original operating conditions. Rather than transforming the object itself, as migration typically does, emulation reconstructs the environment required to run or render the object, which may help maintain aspects of authenticity, usability, and the original look and feel. The extent to which emulation preserves the integrity and reliability of a record, and its suitability relative to alternatives such as migration, depends on organizational policy, the object type, and the availability and accuracy of the emulating software. Note that in general usage 'emulation' can also mean the endeavor to equal or excel others; that ordinary-language sense falls outside its technical meaning here.

Why it matters

Digital records are frequently bound to the hardware and software environments in which they were created. As those environments become obsolete, records that depend on them can become difficult or impossible to render, even when the underlying files remain intact. Emulation matters because it offers a way to keep such material accessible without altering the original object, which can be significant where the object's original look, feel, and behavior are themselves part of what needs to be preserved. This is particularly relevant for complex or interactive digital objects, such as software-dependent files, whose meaning may not survive being converted to another format.

Emulation is one of several strategies for maintaining the usability of digital records over time, and it is often discussed alongside migration. The two approaches differ in what they change: migration typically transforms the object into newer formats, whereas emulation leaves the object unaltered and instead reconstructs the environment needed to run or render it. This distinction has consequences for authenticity and integrity, since preserving an object unchanged may support claims about its reliability as evidence. Whether emulation is the appropriate choice, however, depends on organizational policy, the type of object, and the availability and accuracy of suitable emulating software.

Because emulation depends on software that imitates a legacy environment, its effectiveness is only as strong as that emulating software allows. The degree to which an emulated environment faithfully reproduces the original conditions can vary, and this affects how far the strategy can be relied upon to maintain the usability of a record. For these reasons, decisions about emulation are best framed as part of a broader preservation approach rather than treated as a universal solution.

Who it's relevant to

Digital preservation specialists

Those responsible for keeping digital records usable over time need to weigh emulation against alternatives such as migration. Emulation is especially relevant where an object's original behavior or appearance must be retained, and where transforming the file would risk losing part of its meaning.

Archivists and records managers

Professionals managing records as evidence of activity may consider emulation where preserving an object unaltered supports its authenticity and reliability. The choice of strategy typically depends on organizational policy and the nature of the objects involved, so an understanding of what emulation does and does not change is useful when setting preservation approaches.

Libraries, archives, and museums holding software-dependent material

Institutions that hold software or complex digital objects dependent on obsolete environments may use emulation to provide continued access. Emulation allows such material to be rendered without conversion, which can matter where interactivity or original functionality is significant.

Inside Emulation

Original environment recreation

Emulation involves reproducing the behavior of an original hardware platform, operating system, or software environment so that digital records can be rendered and interacted with as they were originally intended, rather than converting the record itself.

Emulator software layer

A program that mimics the functions of obsolete or unavailable computing environments, allowing legacy file formats and applications to run on current systems. The emulator sits between the preserved record and contemporary hardware.

Preserved original bitstream

Emulation typically relies on retaining the record's original bytes unaltered, so that authenticity and integrity are supported by keeping the source object intact rather than transforming it.

Supporting dependencies

The associated software, drivers, configuration, and sometimes documentation needed to make the original environment function, which often must be captured and retained alongside the record.

Relationship to digital preservation strategy

Emulation is one recognized approach to long-term digital preservation, commonly discussed alongside migration, and is generally selected based on the nature of the record, its usability requirements, and organizational policy.

Common questions

Answers to the questions practitioners most commonly ask about Emulation.

Is emulation the same as migration for digital preservation?

No. Emulation and migration are distinct preservation strategies, though they are sometimes confused. Migration typically involves converting records into newer formats or moving them to newer environments over time, which may alter the original bitstream. Emulation instead seeks to recreate the original operating environment, such as hardware, operating system, or software behavior, so that the original files can be rendered and used without altering them. In practice, many preservation programs treat these as complementary rather than interchangeable approaches, and the choice often depends on the records involved, available resources, and organizational policy.

Does emulation guarantee that a record's authenticity and integrity are preserved?

Not on its own. Emulation can support the usability of a record by reproducing the environment in which it was originally created or rendered, but usability is only one of the properties that make something a trustworthy record. Authenticity, reliability, and integrity typically depend on additional controls, such as documented provenance, metadata, and evidence of an unbroken chain of custody. Emulation may help demonstrate how a record appeared or behaved, but it does not by itself establish that the record is what it purports to be or that it has not been altered. These assurances generally require complementary recordkeeping controls.

When might emulation be preferred over migration for a given set of records?

Emulation is often considered where the original look, feel, or behavior of a record is significant, or where migration risks losing functionality or altering the content in ways that matter for evidential value. This can apply to complex or interactive digital objects whose meaning depends on their original rendering environment. The decision typically depends on the nature of the records, the risks of format conversion, resource availability, and organizational policy, so many programs assess this on a case-by-case basis rather than adopting a single strategy for all holdings.

What needs to be documented to make emulation dependable over time?

Reliable emulation generally depends on capturing and retaining sufficient information about the original environment, including details of the operating system, software dependencies, and configuration required to render the records. Preservation metadata describing the record, its provenance, and its technical requirements is often essential. Without adequate documentation, reconstructing a usable environment later can become difficult or unreliable. The specific documentation needed typically varies with the complexity of the records and the emulation approach chosen.

How does emulation fit within a broader digital preservation program?

Emulation is usually treated as one option within a broader preservation strategy rather than a standalone solution. It is often positioned alongside migration, format management, and storage and integrity controls. Many programs decide which approach to apply based on the characteristics and value of particular records, and some retain the flexibility to combine strategies. Placing emulation within a governed framework, supported by policy, metadata, and defined responsibilities, helps ensure that decisions are defensible and consistent.

What ongoing challenges should organizations anticipate with emulation?

Emulation can require sustained effort to remain viable, because the environments used to run emulators may themselves become obsolete over time. Organizations may need to maintain expertise, address software licensing and legal considerations that can vary by jurisdiction, and periodically reassess whether the emulated environment still functions as intended. Because these dependencies can shift, emulation typically calls for ongoing monitoring and planning rather than a one-time implementation.

Common misconceptions

Emulation and migration are interchangeable ways of preserving digital records.

They are distinct strategies. Migration transforms a record into a new format or environment over time, which can alter the object, while emulation preserves the original bitstream and recreates the environment needed to render it. Each carries different implications for authenticity, cost, and usability, and the appropriate choice typically depends on the record and organizational policy.

Emulation guarantees that a record remains an authentic, reliable record indefinitely.

Emulation can support usability and can help preserve the original bitstream, but authenticity, reliability, integrity, and usability also depend on maintaining the emulator, its dependencies, and appropriate documentation and metadata over time. Emulation is a means of continued access, not by itself a guarantee of a record's evidential qualities.

Once an emulator is in place, no further preservation effort is required.

Emulators and their supporting environments can themselves become obsolete, so ongoing management, testing, and potential re-provisioning are often necessary. Emulation shifts, rather than eliminates, the long-term maintenance burden.

Best practices

Assess whether emulation or an alternative strategy such as migration is more appropriate for a given class of records, based on their usability requirements, complexity, and your organizational preservation policy.

Preserve the original bitstream intact and capture the associated dependencies, configuration, and documentation needed to recreate the original environment.

Maintain metadata that supports authenticity, reliability, integrity, and usability, so that the emulated record can be demonstrated to be what it purports to be.

Test emulated access periodically to confirm that records still render and behave as expected, since emulators and their environments can themselves become obsolete.

Plan for the ongoing maintenance and eventual re-provisioning of emulation environments as part of a broader digital preservation program rather than treating emulation as a one-time step.

Document decisions about why emulation was chosen and how it is implemented, to support accountability and future review as technology and requirements change.