Proprietary file format
format that is not a free and open format
A proprietary file format is a file format of a company, organization, or individual that contains data that is ordered and stored according to a particular encoding-scheme, such that the decoding and interpretation of this stored data is easily accomplished only with particular software or hardware that the company itself has developed. In contrast, an open or free format is a file format that is published and free to be used by everybody.
Some proprietary format may be documented by the developer and released with a note that the format is subject to change without notice, and that the file should only be read or written with libraries provided by the developer. In other cases, the specification of the data encoding format may not be publicly documented at all; in some cases, the format may only be released to those who have signed non-disclosure agreements. A proprietary format can also be a file format whose encoding is in fact published but is restricted through licenses such that only the company itself or licensees may use it.
Proprietary formats are typically controlled by a company or organization for its own benefit, and the restriction of its use by others is ensured through patents or as trade secrets. It is thus intended to give the license holder exclusive control of the technology to the (current or future) exclusion of others.
Typically such restrictions attempt to prevent reverse engineering, though reverse engineering of file formats for the purposes of interoperability is generally regarded as being legal by those who practice it. For example, the US Digital Millenium Copyright Act allows for the reverse-engineering of file formats used for copyright management systems for the purpose of allowing users to exercise their fair use rights to copyrighted media.
As control over a format may be exerted in varying ways and in varying degrees, and documentation of a format may deviate in many different ways from the ideal, there is not necessarily a clear black/white distinction between open and proprietary formats.
The public source identifies “Proprietary file format” as format that is not a free and open format. This brief keeps that definition visible, then builds a research path around Proprietary, file and format.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 8, 2026. The linked authority identifier is Q2720536. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Proprietary file format” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.