Extension Description Author File / Link
ip Internet Protocol Link
jam Joaquim-Andrew-Mats Message Base Proposal Joaquim Homrighausen Download
json Lightweight text-based data interchange format of objects, arrays, and values Douglas Crockford / ECMA / IETF Link
m3u8 UTF-8 extended M3U playlist describing media segments and variant streams for HLS Apple / IETF (RFC 8216) Link
mbox Concatenated e-mail messages in one text file, each introduced by a From line IETF (RFC 4155) Link
mbx MBX Mailbox file format Michael Santovec Download
md Lightweight plain-text markup that converts to HTML John Gruber / CommonMark Link
mime RFC1521: Mechanism for specifying and describing the format of Internet message bodies Various Link
RFC1522: Message header extensions for non-Ascii text Various Link
MIME Overview Mark Grand Download
msg Outlook MSG file format Peter Fiskerstrand Download
ndjson Text format with one JSON value per line, used for streaming and record-oriented data (also .jsonl) NDJSON specification contributors Link
netscape Netscape Cache FAT.DB Francois Crevola Deprecated resource Link
oogl Web Object Oriented Graphics Library Deprecated resource Link
opus Open, low-latency, royalty-free lossy audio codec, typically carried in Ogg IETF / Xiph.Org Link
p12 Password-protected bundle of private keys and certificates; same format as .pfx RSA Laboratories / IETF Link
pab MS Exchange Personal Address Book Format Hans Dijkema Download
pem Text encoding for X.509 certificates, keys, and other cryptographic structures IETF (S. Josefsson, S. Leonard) Link
pkt PKT mail file format Caliban Tiresias Darklock Deprecated resource Download
ppp Point to Point Protocol Link
qml Quick Markup Language Quicka Ltd. Deprecated resource Link
qwk QWK Mail Packet Files v1.6 Patrick Y. Lee Download
rss Syndication file format Deprecated resource Link
sdml Spacial Data Modeling Language Silicon Graphics Deprecated resource Link
sdxf Structured Data Exchange Format (SDXF) M. Wildgrube Link
sgml Standard Generalized Markup Language (SGML) Link
sqd Squish message base files .SQD & .SQI SCI Communications Deprecated resource Download
svf Simple Vector Format SoftSource Link
swf SWF File Format Specification Macromedia, Incorporated Deprecated resource Download
Macromedia Flash File Format (SWF) Macromedia, Incorporated Deprecated resource Link
tags MIME Tag types site John Lines Deprecated resource Link
tcp Transmission Control Protocol Link
tcp-ip Microsoft Windows NT 3.5/3.51/4.0 TCP/IP Implementation Details, TCP/IP Protocol Stack and Services, Version 2.0 (Word) Dave MacDonald Download
tnef Transport-Neutral Encapsulation Format (TNEF) Download
toc Eudora Table of Contents Deprecated resource Link
torrent Bencoded dictionary describing shared files, piece hashes, and tracker URLs Bram Cohen / BitTorrent.org Link
ts Source code of the TypeScript language, a typed superset of JavaScript Microsoft Link
udp User Datagram Protocol Link
url Internet Explorer URL files Edward Blake Download
uuencode UU-encoded data Jim Cameron Download