QR Anvil

QR Anvil is live at qr-anvil.com. The source code is in a public repo on GitHub (source-available, PolyForm Noncommercial license).

QR Anvil is a free QR code generator with two modes. Direct codes encode your data straight into the QR image — they work offline, with nothing in between. Tracked codes redirect through a short URL first, so every scan is logged with analytics and the destination stays editable after the code is printed.

The practical upshot: print a tracked QR on a flyer today, and you can change where it points tomorrow — and see how many people scanned it, from where, on what device.

Features

• Two code modes — Direct (encoded, offline-friendly) and Tracked (redirect + scan analytics).
• Scan analytics for tracked codes — device, OS, browser, and geo captured server-side; destination editable after the code is printed.
• Eight QR types — URL, Wi-Fi, vCard, Email, SMS, WhatsApp, PDF, and plain text.
• Three download formats — PNG, SVG, and PDF, all generated in the browser.
• Styled QR rendering in the browser via qr-code-styling (canvas / SVG), with an optional centre logo that is validated and resized.
• QR scanner — a page that reads QR codes from the camera or from an uploaded image (@zxing/browser).
• Accounts via Clerk authentication with webhook-based user sync. URL codes and PNG downloads need no account; tracked codes and SVG / PDF downloads need a free account.

How it is built

• Scan redirect that answers first and logs after — the short-URL route returns the 302 redirect at once. Then Next.js after() records the device, OS, browser, geo (from proxy headers), and a truncated IP. Only http(s) destinations are accepted.
• Tracked-code reservations — a short code is held on a one-hour lease, so the live preview scans correctly before you save. Expired claims stay as tombstones, so a code can never point to another user’s destination. Tests cover retries and concurrent activation.
• Rate limits — three sliding-window limits on Upstash Redis (general API, reservation create, reservation change).
• SEO — JSON-LD structured data, a tested sitemap, how-to guides, per-type landing pages, /llms.txt, and security headers.
• Tests — 98 automated test cases across 11 files with Vitest.
• Deployment — a multi-stage Dockerfile (Next.js standalone output) on Coolify on Hetzner Cloud, with prisma migrate deploy at container start, a /api/health endpoint, and Cloudflare in front.
• Backups — hourly PostgreSQL backups to Backblaze B2. A restore test passed on 2026-09-14.

Summary

A two-mode QR generator built with Next.js.

• Client-side QR rendering (qr-code-styling); PNG / SVG / PDF export (pdf-lib) all generated in the browser.
• Tracked codes: a short-URL redirect that answers first and logs scan analytics after, with a destination you can edit after printing.
• Eight content types, from URLs to Wi-Fi to vCards, and a browser QR scanner.
• Upstash Redis rate limits, 98 Vitest test cases, and a reservation design with lease and tombstones.
• Clerk auth, Prisma + PostgreSQL; deployed with Docker on Coolify (Hetzner Cloud), with hourly backups and a tested restore.