QR code glossary
Plain-English definitions of the QR-code terms that come up when you build, print, or troubleshoot a code.
Dynamic QR code
A QR whose printed pattern points at a redirect service, with the destination editable at any time.
Dynamic QR codes encode a short link (e.g. r.kaiqr.com/abc123) into the dot pattern. When someone scans, the redirect service looks up the current destination and forwards the scanner there. Because the printed pattern never changes, the QR works forever; because the destination is stored server-side, you can update it whenever the link, file, or campaign needs to change — no re-printing.
Static QR code
A QR whose printed dot pattern encodes the destination directly. Cannot be edited after printing.
Static QR codes embed the destination URL (or vCard, or WiFi credentials) inline in the dot matrix — there is no redirect step. They're simpler and don't need a hosted service to keep working, but the moment the destination URL changes, every printed copy of the static QR is dead. KaiQR's free Website QR is static. Anything where the destination might change later (menu, price list, contact details, seasonal promotion) should be a dynamic QR instead.
QR code
A two-dimensional barcode that encodes text, a URL, or a vCard, readable by any modern phone camera.
Quick Response codes were invented in 1994 by Denso Wave for tracking automotive parts. The pattern is a square grid of black and white modules with three large finder squares in the corners. Phones use those finder squares to align scanning, then decode the inner pattern into text. Camera apps on iOS 11+ and Android 8+ scan QR codes natively — no separate app needed.
vCard
A standard file format (.vcf) for sharing a contact card. A vCard QR encodes one inline so scanners can save the contact in a single tap.
vCard is the IETF standard for digital business cards (RFC 6350). A QR-encoded vCard can include name, organisation, title, phone, email, address, website, and a photo URL. When someone scans the QR, their phone offers to save all of those fields straight into Contacts — much faster than typing details from a paper card. KaiQR's vCard type is dynamic: change your phone number or job title in the dashboard and the QR's destination updates without reprinting your business cards.
Short link
A short URL (like r.kaiqr.com/abc123) that redirects to a longer destination URL.
Short links are how dynamic QR codes work. Instead of encoding the long destination URL into the QR pattern, the pattern encodes a compact short link. On scan, the short link's redirect service looks up the destination and forwards the scanner. KaiQR uses 6-character base32 codes (≈10⁹ possible codes per prefix) so the visible URL stays short enough to fit on a poster footer or business card.
Redirect service
The server that turns a short link into a destination URL when the QR is scanned.
A redirect service receives the short-link request, looks up the current destination in its database, logs the scan event for analytics, and returns a 302 redirect to the destination. Speed matters — every millisecond of redirect latency adds friction at scan time. KaiQR's redirect runs on Cloudflare Workers at every edge node worldwide, so the round-trip from scan to destination is under 40 ms in most regions.
Error correction (EC) level
Redundancy built into a QR matrix so it still scans with 7%, 15%, 25%, or 30% of the pattern damaged.
QR codes use Reed-Solomon error correction across four levels: L (~7%), M (~15%), Q (~25%), H (~30%). Higher EC means more redundant data, which means a denser pattern (more modules) for the same payload. Higher EC also means a logo can sit in the centre of the QR without breaking scannability — the surrounding redundancy reconstructs the dots the logo covers. KaiQR uses level H for QRs that include a logo, level M otherwise.
Scan
One event of a phone reading the QR and triggering the redirect service.
A scan is the unit of analytics for any dynamic QR. KaiQR records the timestamp, country, city, device class (phone / tablet / desktop), browser, and referrer for every scan — all derived from Cloudflare-provided fields, with no IP collection or personal data. The dashboard shows scan counts over time, top countries, top devices, and per-QR drill-downs.
Finder pattern
The three large square markers in three corners of every QR code. Phones use them to align the scan.
Each finder pattern is a 7×7 module square: an outer black border, a white ring, and a black centre. Three of them sit at three corners of the QR (top-left, top-right, bottom-left); the fourth corner has a smaller alignment pattern instead. The asymmetry tells the scanner which way is up, even if the QR is rotated, mirrored, or photographed at an angle. Touching or styling the finder patterns breaks scanning faster than damage anywhere else in the matrix.
Payload
The actual data encoded in the QR pattern — typically a URL for dynamic QRs, or vCard / WiFi data for static QRs.
For a dynamic QR, the payload is the short link (e.g. r.kaiqr.com/abc123) — the destination is stored separately on the redirect service. For a static QR, the payload is the destination itself: the full URL, the BEGIN:VCARD…END:VCARD block, the WIFI:T:WPA;S:…;P:…;; string. Larger payloads need denser QR patterns, so for printed materials a dynamic QR with its short-link payload always produces a cleaner, more reliable code than a static QR with the full URL inline.
Edge redirect
A redirect that resolves at a CDN edge node geographically close to the scanner — sub-50 ms latency, survives any single data centre outage.
Edge redirects run on globally-distributed compute (Cloudflare Workers, Vercel Edge Functions, AWS Lambda@Edge) — the request resolves at the nearest data centre to the scanner, rather than bouncing through a central origin server. The round-trip from QR scan to destination drops below 50 ms in most regions, and a single data centre going down doesn't break scans worldwide. KaiQR's redirect service is edge-deployed for exactly these reasons.
Short code
The unique identifier in a short link's path (e.g. `abc123` in `r.kaiqr.com/abc123`). Maps one-to-one with a QR.
When KaiQR creates a dynamic QR, it mints a unique short code — 6 random characters from a 32-character alphabet (≈10⁹ possibilities), prefixed with `p_` for in-progress preview QRs. The short code is what the QR pattern actually encodes; the redirect service uses it as the database key when looking up the destination on scan. Short codes never get reused, even if a QR is deleted, so analytics history stays clean.