EML

DOCX is the default file format for Microsoft Word documents since Office 2007, built on the Open XML standard developed by Microsoft and standardized by ISO. It stores document content, formatting, images, tables, and metadata in a compressed ZIP archive containing XML files. DOCX is the dominant word processing format worldwide, supported by Microsoft Word, Google Docs, LibreOffice, and virtually all modern office software.

HTML (HyperText Markup Language) is the standard markup language for creating web pages and web applications, maintained by the W3C. It defines the structure and content of documents using elements and tags, working alongside CSS for visual styling and JavaScript for interactivity. HTML is rendered by web browsers into the visual pages users see, and is the universal output format for documents published on the internet.

Markdown is a lightweight plain-text markup language created by John Gruber in 2004 to make writing formatted content for the web as easy as possible. It uses minimal punctuation-based syntax to define headings, emphasis, links, images, lists, and code blocks that convert cleanly to HTML. Markdown is the dominant format for README files, software documentation, technical blogs, and static site generators across the entire software industry.

ODT (OpenDocument Text) is an open standard document format developed by OASIS for word processing, used as the native format by LibreOffice Writer and Apache OpenOffice Writer. It stores document content, styles, images, and metadata as XML in a ZIP archive, ensuring full transparency and long-term accessibility without vendor lock-in. ODT is also supported for import and export by Microsoft Word and Google Docs.

PDF (Portable Document Format) was created by Adobe in 1992 and has become the worldwide standard for sharing documents with precisely fixed layouts. It preserves fonts, images, vector graphics, and formatting identically across every operating system, device, and printer. PDF supports digital signatures, encryption, interactive forms, and embedded multimedia, making it essential for official documents, contracts, reports, and professional publications.

reStructuredText (RST) is a plain-text markup language widely used for technical documentation in the Python programming ecosystem. It is the default documentation format for Python projects and the native input format for the Sphinx documentation generator, which produces HTML, PDF, ePub, and man pages. RST supports complex cross-references, footnotes, directives, and extensions, making it well-suited for large, structured documentation projects.

RTF (Rich Text Format) is a document interchange format developed by Microsoft in 1987 to allow formatted text to be shared across different word processors and operating systems. It encodes text formatting such as fonts, colors, bold, italic, and paragraph alignment using ASCII escape sequences, making it readable by virtually any word processor. RTF remains widely used as a compatibility format when the recipient's software is unknown.

TXT (Plain Text) is the simplest possible file format, containing only unformatted characters encoded in ASCII or Unicode with no styling, images, or structural metadata. It is universally compatible with every operating system, programming language, text editor, and application that handles text. Plain text is used for source code, configuration files, README documents, log files, and any situation where maximum simplicity and portability are required.