vCard Contact Format
Telephony and messaging apps exchange contacts as `.vcf` files — parsed in MMS (MMS vCard attachments), QR contact cards, and SIP presence. TEL property formatting ties directly to E.164.
What It Defines
Text-based contact card format (`.vcf`): `BEGIN:VCARD` envelope, structured properties (FN, N, TEL, EMAIL, ADR, ORG), parameter qualifiers (TYPE=CELL, PREF), and VERSION 3.0/4.0 syntax. MIME type: `text/vcard`. Standard payload for MMS contact sharing and address book import/export.
Canonical (Normative)
Convenient (Practical)
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
Every phone number your app touches — Twilio, AWS SNS, WhatsApp, SIP — uses E.164. Getting number formatting and parsing right (libphonenumber patterns) requires understanding CC/NDC/SN structure.
MMS is still widely used for group messaging (iMessage fallback on non-Apple devices), marketing images, and vCards. Understanding MM7 (application-to-MMSC API) is needed when integrating with carrier MMS gateways.
SMS is how billions of people receive OTP codes, alerts, and notifications. Understanding PDU format, encoding (GSM-7 vs UCS-2), and concatenation is essential for any platform sending SMS at scale via Twilio, AWS SNS, or direct SMPP.