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:
Imaging
- APNG: It allows for animated PNG files that work similarly to animated GIF files.
- AVIF: An image format using AV1 compression.
- FLIF: Free Lossless Image Format.
- GBR: a 2D binary vector image file format, the de facto standard in the printed circuit board (PCB) industry
- GIF: CompuServe's Graphics Interchange Format (openly published specification, but patent-encumbered by a third party; became free when patents expired in 2004)
- JPEG 2000: an image format standardized by ISO/IEC
- MNG: moving pictures, based on PNG
- OpenEXR: a high dynamic range imaging image file format, released as an open standard along with a set of software tools created by Industrial Light and Magic (ILM).
- PNG: a raster image format standardized by ISO/IEC
- SVG: a vector image format standardized by W3C
- WebP: image format developed by Google
- XPM: image file format used by the X Window System
Audio
- ALAC: lossless audio codec, previously a proprietary format of Apple Inc.
- FLAC: lossless audio codec
- DAISY Digital Talking Book: a talking book format
- Musepack: an audio codec
- MP3: lossy audio codec, previously patented
- Ogg: container for Vorbis, FLAC, Speex and Opus (audio formats) & Theora (a video format), each of which is an open format
- Opus: a lossy audio compression format developed by the IETF. Suitable for VoIP, videoconferencing (just audio), music transmission over the Internet and streaming applications (just audio).
- Speex: speech codec
- Vorbis: a lossy audio compression format.
- WavPack: "Hybrid" (lossless/lossy) audio codec
Video
- Dirac: a video compression format supporting both lossless and lossy compression
- Matroska (mkv): container for all type of multimedia formats (audio, video, images, subtitles)
- WebM: a video/audio container format
- Theora: a lossy video compression format.
Archiving & Compression Supported Formats
.7z - Open-source file format. Used by 7-Zip.
.ar - The traditional archive format on Unix-like systems, now used mainly for the creation of static libraries.
.arc - Open-source file format developed by Bulat Ziganshin. A "FreeArc Next" version is under development which includes Zstandard support.
.arj - Competitor to PKZIP in the 1990s, offered better multi-part archive handling.
.bz2 - An Open-source, patent- and royalty-free compression format. The compression algorithm is a Burrows–Wheeler transform followed by a move-to-front transform and finally Huffman coding.
.cpio - RPM files consist of metadata concatenated with (usually) a cpio archive. Newer RPM systems also support other archives, as cpio is becoming obsolete. cpio is also used with initramfs.
.dar - Open-source file format. Files are compressed individually with either gzip, bzip2 or lzo.
.gz - GNU Zip, the primary compression format used by Unix-like systems. The compression algorithm is Deflate, which combines LZSS with Huffman coding.
.iso - An archive format originally used mainly for archiving and distribution of the exact, nearly-exact, or custom-modified contents of an optical storage medium such as a CD-ROM or DVD-ROM. However, it can be used to archive the contents of other storage media, selected partitions, folders, and/or files. The resulting archive is typically optimized for convenient rendering to (re-)writable CD or DVD media.
.jar - Java archive, compatible with ZIP files.
.lz - An alternate LZMA algorithm implementation, with support for checksums and ident bytes.
.lz4 - Algorithm developed by Yann Collet, designed for very high (de)compression speeds. It is an LZ77 derivative, without entropy encoding.
.lzma - The LZMA compression algorithm as used by 7-Zip.
.lzo - An implementation of the LZO data compression algorithm.
.phar - A package format to enable distribution of applications and libraries by bundling many PHP code files and other resources (e.g. images, stylesheets, etc.) into a single archive file.
.rar - A proprietary archive format, second in popularity to .zip files.
.rz - An implementation of the LZO data compression algorithm.
.shar - A self-extracting archive that uses the Bourne shell (sh).
.sz - A compression format developed by Google, and open-sourced in 2011. Snappy aims for very high speeds, reasonable compression, and maximum stability rather than maximum compression or compatibility with any other compression library. It is an LZ77 derivative, without entropy encoding.
.tar - A common archive format used on Unix-like systems. Generally used in conjunction with compressors such as gzip, bzip2, compress or xz to create .tar.gz, .tar.bz2, .tar.Z or tar.xz files.
.xz - A compression format using LZMA2 to yield high compression ratios. The LZMA algorithm is an LZ77 derivative, with entropy encoding in the form of range encoding.
.zip - ZIP is an archive file format that supports lossless data compression.