The Open Standard for Live Business Cards
LiveCard Exchange (LCX) is an interoperable protocol that lets digital business cards update in real time. Share once, stay current forever — across any app, any platform.
What is LCX?
LCX defines everything needed for business cards to be shared via QR codes and updated live from a server — the data model, the visual layout, the transfer protocol, and the caching behavior.
For Card Providers
Build a platform where users create and host digital business cards. LCX tells you exactly what data to serve, what endpoints to expose, and how to format the QR codes.
For Card Consumers
Build an app that scans, stores, and displays business cards. LCX tells you what data to expect, how to render layouts, and how to keep cards fresh via polling.
What the Standard Covers
LCX 1.0 is a comprehensive specification with 11 normative sections and 5 appendices. Here are the core pillars.
Card Data Model
A JSON schema covering identity, contacts, addresses, social links, custom fields, and media assets.
QR Code Encoding
A compact JSON payload format for QR codes, with optional snapshot data for instant preview before the server is reached.
Media Assets
Profile photos, background images, and logos with BlurHash placeholders, resolution guidance, and inline fallbacks.
Layout & Positioning
An absolute-positioning canvas system (1000 x 600 units) with text, image, shape, divider, QR code, and icon elements.
Update Server Protocol
A REST API spec with ETag caching, conditional requests, structured error responses, CORS, and rate limiting.
Auth, Caching & Security
Optional bearer/query token auth, TTL-based polling, offline fallback requirements, and TLS 1.2+ enforcement.
How It Works
A typical LCX exchange in four steps.
Create a Card
A Card Provider builds the card payload with identity data, media, and layout — then hosts it at an Update Endpoint.
Share via QR
The provider generates a QR code containing the Card URI, card ID, and an optional snapshot for instant preview.
Scan & Fetch
A Card Consumer scans the QR code, fetches the full payload from the Update Endpoint, and caches it locally.
Live Updates
The consumer periodically re-fetches the card using ETags and TTL. The card stays current — even if the owner changes jobs.
Technical Details
Data Format & Transport
- •JSON payloads with camelCase field names
- •Custom MIME type:
application/vnd.lcx.card+json - •REST endpoint:
GET /lcx/v1/cards/{cardId} - •ISO 8601 timestamps, UUID v4 identifiers
- •HTTPS with TLS 1.2+ required
Versioning & Extensibility
- •Every payload carries an
lcxVersionfield - •Unknown fields are silently ignored (forward-compatible)
- •Custom extensions via
x-prefixed fields - •Semantic versioning: patch / minor / major
- •RFC 2119 conformance language throughout
Read the Full Specification
The complete LCX 1.0 document with all 11 sections, JSON Schema, example payloads, and HTTP exchange examples.
View Specification