Nearly 40 years on, HDF4 receives one final official release focused on security, stability, and long-term use.
HDF4 has supported scientific computing for nearly four decades. It has powered remote sensing systems, Earth science applications, aerospace work, and long-lived research and operational systems. HDF5 has been the focus of active development for many years, but HDF4 remains embedded in real applications and important scientific archives.
The HDF Group has now released HDF4 4.0, the final official release of the HDF4 library.
This is not a nostalgia release. It is a stewardship release.
Our goal was straightforward: leave HDF4 in the best possible condition for the users and archives that will continue to depend on it.
A release built for continued use
HDF4 4.0 does not introduce a new generation of features. It concentrates on the work that matters most at this stage of a mature software product: security, stability, and maintainability.
The release addresses a substantial number of memory-management issues and security vulnerabilities throughout the codebase. These corrections are especially important for applications that process HDF4 files from external or untrusted sources, but they also improve reliability across all deployments.
Reading SZIP-compressed data and metadata is also more robust. We corrected behavior that could depend incorrectly on whether the system had access to the full SZIP library, a decoder-only library, or no SZIP library at all.
We also strengthened error handling and resource cleanup across the test suite and supporting tools. The result is software that is easier to maintain and a code base better prepared for long-term use.
These changes are not flashy. They are exactly what a long-lived scientific data format needs.
An upgrade that requires care
Some of the security corrections required breaking changes. Existing applications should therefore be tested carefully, and every organization planning an upgrade should review the HDF4 4.0 RELEASE.txt file first.
HDF4 4.0 also makes CMake the only supported build system.
Fortran on 64-bit platforms remains a particular concern. Most configurations should be treated as unsupported, even though individual compiler-platform combinations may work. Organizations that depend on the HDF4 Fortran interface may need to remain on HDF4 3.1 and validate any attempted move to 4.0 within their own build and deployment environments.
The end of official releases, not the end of HDF4
With version 4.0, HDF4 enters maintenance-only status. No further official HDF4 releases are planned.
For new projects, we continue to recommend HDF5, which remains under active development and support. For existing HDF4 users, version 4.0 provides a more stable and secure endpoint for long-term deployment and archival use.
That distinction matters. Mature infrastructure does not stop mattering when active feature development ends. Scientific organizations still need to operate established systems, preserve older data, and reproduce earlier results. HDF4 4.0 is intended to make that work safer and more dependable.
Learn More
- Review the HDF4 4.0 RELEASE.txt file for details about compatibility changes and upgrade considerations.
- Visit the HDF4 product page for documentation and resources.
- Contact the HDF Help Desk for assistance with upgrading or maintaining HDF4-based applications.
- Join the discussion on the HDF Community Forum.
We encourage all HDF4 users to review the breaking changes documented in RELEASE.txt and, if possible, upgrade to HDF4 4.0.
Nearly 40 years of community work
HDF4 reached this point through sustained community effort.
Developers contributed code. Researchers tested it against real scientific problems. Organizations reported issues and supported its continued maintenance. Users supplied feedback and carried HDF4 into disciplines and systems far beyond its original setting.
We thank everyone who helped make HDF4 one of the most widely adopted scientific data formats of its era.
HDF4 4.0 is a final official release, not a ceremonial goodbye. HDF4 still has data to serve and archives to protect. Our responsibility was to leave it ready for that work.
Before upgrading, review the HDF4 4.0 RELEASE.txt file for compatibility details. Documentation is available through the HDF4 product page, with additional help through the HDF Help Desk and the HDF Community Forum.