Open standard in the context of C99

Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The World Wide Web Consortium's XML 1.0 Specification of 1998 and several other related specifications—all of them free open standards—define XML.

The design goals of XML emphasize simplicity, generality, and usability across the Internet. It is a textual data format with strong support via Unicode for different human languages. Although the design of XML focuses on documents, the language is widely used for the representation of arbitrary data structures, such as those used in web services.

Matroska (styled Matroška) is a project to create a container format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file. The Matroska Multimedia Container is similar in concept to other containers like AVI, MP4, or Advanced Systems Format (ASF), but is an open standard.

Matroska file extensions are .mkv for video (which may include subtitles or audio), .mk3d for stereoscopic video, .mka for audio-only files (which may include subtitles), and .mks for subtitles only.

An open file format is a file format for storing digital data, defined by an openly published specification usually maintained by a standards organization, and which can be used and implemented by anyone. An open file format is licensed with an open license.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 file formats, closed file formats are considered trade secrets.

Depending on the definition, the specification of an open format may require a fee to access or, very rarely, contain other restrictions. The range of meanings is similar to that of the term open standard.

Scalable Vector Graphics (SVG) is an XML-based vector graphics format for defining two-dimensional graphics, having support for interactivity and animation. The SVG specification is an open standard developed by the World Wide Web Consortium since 1999.

SVG images are defined in a vector graphics format and stored in XML text files. SVG images can thus be scaled in size without loss of quality, and SVG files can be searched, indexed, scripted, and compressed. The XML text files can be created and edited with text editors or vector graphics editors, and are rendered by most web browsers. SVG can include JavaScript, potentially leading to cross-site scripting.

Online help is a form of user assistance that provides topic-oriented, procedural or reference information designed to assist in using a software application, web application or operating system. Online help linked to the application's state (what the user is doing) is called Context-sensitive help.

The help information can be created using help authoring tools or component content management systems and can be delivered in a wide variety of proprietary and open-standard formats. Help of this kind has largely replaced printed documentation.

Gecko is a browser engine developed by Mozilla. It is used in the Firefox browser, the Thunderbird email client, and in a discontinued state on AOL's Netscape 6, Netscape 7, Netscape Browser and Netscape Navigator 9; this is alongside many other projects.

Gecko is designed to support open Internet standards, and is used by different applications to display web pages and, in some cases, an application's user interface itself (by rendering XUL). Gecko offers a rich programming API that makes it suitable for a wide variety of roles in Internet-enabled applications, such as web browsers, content presentation, and client/server.

Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) of the European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU).

Extensible Messaging and Presence Protocol (abbreviation XMPP, originally named Jabber) is an open communication protocol designed for instant messaging (IM), presence information, and contact list maintenance. Based on XML (Extensible Markup Language), it enables the near-real-time exchange of structured data between two or more network entities. Designed to be extensible, the protocol offers a multitude of applications beyond traditional IM in the broader realm of message-oriented middleware, including signalling for VoIP, video, file transfer, gaming and other uses.

Unlike most commercial instant messaging protocols, XMPP is defined in an open standard in the application layer. The architecture of the XMPP network is similar to email; anyone can run their own XMPP server and there is no central master server. This federated open system approach allows users to interoperate with others on any server using a 'JID' user account, similar to an email address. XMPP implementations can be developed using any software license and many server, client, and library implementations are distributed as free and open-source software. Numerous freeware and commercial software implementations also exist.

JSON (JavaScript Object Notation, pronounced /ˈdʒeɪsən/ or /ˈdʒeɪˌsɒn/) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of name–value pairs and arrays (or other serializable values). It is a commonly used data format with diverse uses in electronic data interchange, including that of web applications with servers.

JSON is a language-independent data format. It was derived from JavaScript, but many modern programming languages include code to generate and parse JSON-format data. JSON filenames use the extension .json.

Rich Communication Services (RCS) is a communication protocol standard for instant messaging, primarily for mobile phones, developed and defined by the GSM Association (GSMA). It is a replacement of SMS and MMS on cellular networks with more modern features including high resolution image and video support, typing indicators, file sharing, and improved group chat functionality. Development of RCS began in 2007 but early versions lacked features and interoperability; a new specification named Universal Profile was developed and has been continually rolled out since 2017.

RCS has been designed as an industry open standard to provide improved capabilities over basic text messaging, based on the Internet Protocol (IP). Its development has also been supported by mobile network operators to remain relevant in customer experience in response to over-the-top (OTT) chat apps and services. Additional features of RCS include presence information, location and multimedia sharing, video calling, and operation over mobile data or Wi-Fi, natively integrated in mobile phones without requiring the download of third-party apps.

The Khronos Group, Inc. is an open standards organization that is driven by over 180 member companies developing, publishing and maintaining royalty-free interoperability standards for 3D graphics, virtual reality, augmented reality, parallel computation, vision acceleration and machine learning. The open standards and associated conformance tests enable software applications and middleware to effectively harness authoring and accelerated playback of dynamic media across a wide variety of platforms and devices. The group is based in Beaverton, Oregon.

The JPEG XL Image Coding System (JPEG XL, sometimes shortened to JXL) is an image format that supports both lossy and lossless compression. It was developed by the Joint Photographic Experts Group (JPEG), Google and Cloudinary. It is a free and open standard defined by ISO/IEC 18181. The standard consists of four parts that cover the Core coding system, File format, Conformance testing, and Reference software, respectively.

JPEG XL features a lossy compression mode called VarDCT built on block-based transform coding, which is similar to — but significantly improves and expands upon — the compression method of JPEG, and a modular mode that allows different features of the format to be combined in a "modular" way. Modular mode can be used either for lossless image compression, similar to PNG, or as a means to achieve lossy compression in a different way from VarDCT.

Bluesky (abbreviated as Bsky) is an American microblogging social media service. Users can share short posts containing text, images, and videos. It is owned by Bluesky Social PBC, a benefit corporation based in the United States.

Bluesky was developed as a reference implementation of the AT Protocol, an open communication protocol for distributed social networks. Bluesky Social promotes a composable user experience and algorithmic choice as core features of Bluesky. The platform offers a "marketplace of algorithms" where users can choose or create algorithmic feeds, user-managed moderation and labelling services, and user-made "starter packs" that allow users to quickly follow a large number of related accounts within a community or subculture. The AT Protocol offers a domain-name–based handle system within Bluesky, allowing users to self-verify an account's legitimacy and identity by proving ownership of a domain name.