An open format is a file format for storing digital data, defined by a published specification usually maintained by a standards organization, and which can be used and implemented by anyone. For example, an open format can be implemented by both proprietary and free and open-source software, using the typical software licenses used by each. In contrast to open formats, closed formats are considered trade secrets. Open formats are also called free file formats if they are not encumbered by any copyrights, patents, trademarks or other restrictions (for example, if they are in the public domain) so that anyone may use them at no monetary cost for any desired purpose.
- Sun Microsystems defines the criteria for open formats as follows:
- The format is based on an underlying open standard
- The format is developed through a publicly visible, community driven process
- The format is affirmed and maintained by a vendor-independent standards organization
- The format is fully documented and publicly available
- The format does not contain proprietary extensions
Within the framework of Open Government Initiative, the federal government of the United States adopted the Open Government Directive, according to which: "An open format is one that is platform independent, machine readable, and made available to the public without restrictions that would impede the re-use of that information".
State of Minnesota
The State of Minnesota defines the criteria for open, XML-based file formats as follows:
- The format is interoperable among diverse internal and external platforms and applications
- The format is fully published and available royalty-free
- The format is implemented by multiple vendors
- The format is controlled by an open industry organization with a well-defined inclusive process for evolution of the standard
Commonwealth of Massachusetts
The Commonwealth of Massachusetts "defines open formats as specifications for data file formats that are based on an underlying open standard, developed by an open community, affirmed and maintained by a standards body and are fully documented and publicly available."
The Enterprise Technical Reference Model (ETRM) classifies four formats as "Open Formats":
- OASIS Open Document Format For Office Applications (OpenDocument) v. 1.1
- Ecma-376 Office Open XML Formats (Open XML)
- Hypertext Document Format v. 4.01
- Plain Text Format
The Linux Information Project
According to The Linux Information Project, the term open format should refer to "any format that is published for anyone to read and study but which may or may not be encumbered by patents, copyrights or other restrictions on use" - as opposed to a free format which is not encumbered by any copyrights, patents, trademarks or other restrictions.
Examples of open formats
Open formats include:
- PNG — a raster image format standardized by ISO/IEC
- FLAC — lossless audio codec
- WebM — a video/audio container format
- HTML — HyperText Markup Language (HTML) is the main markup language for creating web pages and other information that can be displayed in a web browser.
- gzip — for compression
- CSS — style sheet format usually used with (X)HTML, standardized by W3C