(registered 2026-03-17, last updated 2026-03-17)

Media type name: application

Media subtype name: vnd.hdfgroup.hdf4

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: binary

Security considerations: HDF4 is a binary container format that can hold large, complex datasets and metadata. Implementations should treat files as untrusted input and defend against:

- memory corruption and parser vulnerabilities in HDF4 libraries,
- resource exhaustion (very large declared dimensions, many objects,
deeply nested or highly fragmented structures),
- decompression-related resource exhaustion if compression is used.

HDF4 does not provide built-in mechanisms for confidentiality, integrity, or authentication; if such services are required, they must be provided externally (e.g., via transport security or encryption at rest).

Interoperability considerations: Filename extensions are not a reliable indicator of the underlying format: the extension “.hdf” is commonly used for both HDF4 and HDF5 content (and may also be used for other HDF-family files). Implementations SHOULD identify content by inspecting the on-disk format signature rather than relying on extensions. HDF4 files begin with the 4‑byte header signature 0x0E031301 at offset 0. HDF5 files contain the 8‑byte signature 0x894844460D0A1A0A at offset 0, or at offset 512 and successive powers-of-two multiples (to allow an optional user block). If the expected signature is not present, the content SHOULD be treated as unknown or in a different format rather than inferred from the filename.

Published specification: HDF Specification and Developer’s Guide (The HDF Group).

https://zenodo.org/records/13754936

Applications which use this media: Scientific/engineering data tools using the HDF4 library, including HDFView and domain-specific toolchains.

Fragment identifier considerations: none

Restrictions on usage: none

Additional information:

1. Deprecated alias names for this type: application/x-hdf (historic, unregistered)
2. Magic number(s): Hex (offset 0): 0E 03 13 01 (This is the 4-byte HDF file header signature.)
3. File extension(s): .hdf (common), .h4, .hdf4 (also seen)
4. Macintosh file type code: none known
5. Object Identifiers: none

Person to contact for further information:

1. Name: The HDF Group
2. Email: help&hdfgroup.org

Intended usage: COMMON

Author/Change controller: The HDF Group