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A container format (informally, sometimes called a wrapper) or metafile is a
file format A file format is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Standard (metrology), an object that bears ...
that allows multiple data streams to be embedded into a single
file File or filing may refer to: Mechanical tools and processes * File (tool) A file is a tool used to remove fine amounts of material from a workpiece. It is common in woodworking, metalworking, and other similar trade and hobby tasks. Most are ...
, usually along with
metadata Metadata is "data Data (; ) are individual facts, statistics, or items of information, often numeric. In a more technical sense, data are a set of values of qualitative property, qualitative or quantity, quantitative variable (research), v ...

metadata
for identifying and further detailing those streams. Notable examples of container formats include
archive file In computing, an archive file is a computer file that is composed of one or more files along with metadata. Archive files are used to Linker (computing), collect multiple data files together into a single file for easier Software portability, por ...
s (such as the ZIP format) and formats used for multimedia playback (such as
Matroska The Matroska Multimedia Container is a free, open-standard container format, a file format ogg-file: 154 kilobytes. A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are use ...

Matroska
, MP4, and AVI). Among the earliest
cross-platform In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and soft ...

cross-platform
container formats were
Distinguished Encoding Rules X.690 is an ITU-T The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications and Information Communication Technology such as X.509 for cybersecurity, Y.3172 and Y.3173 for machine learning, and H.264/MPE ...
and the 1985
Interchange File Format Interchange File Format (IFF), is a generic container format (digital), container file format originally introduced by the Electronic Arts company in 1985 (in cooperation with Commodore International, Commodore) in order to facilitate transfer of ...
.


Design

Although containers may identify how data or metadata is encoded, they do not actually provide instructions about how to decode that data. A program that can open a container must also use an appropriate
codec A codec is a device or which encodes or a or . ''Codec'' is a of coder/decoder. In electronic communications, an endec is a device which acts as both an encoder and a decoder on a signal or data stream, and hence is a type of codec. ''Endec' ...
to decode its contents. If the program doesn't have the required algorithm, it can't use the contained data. In these cases, programs usually emit an error message that complains of a missing codec, which users may be able to acquire. Container formats can be made to wrap any kind of data. Though there are some examples of such file formats (e.g.
Microsoft Windows Microsoft Windows, commonly referred to as Windows, is a group of several proprietary {{Short pages monitor