---
title: "QR Code Specifications, Print Guide & Privacy Manifesto"
description: "In-depth guide to QR code printing standards, DPI calculation, error correction levels (ECC), vector SVG export, and client-side privacy architecture."
url: "https://qrstudiofree.com/about/"
markdownUrl: "https://qrstudiofree.com/about/index.md"
language: "en"
site: "QR Studio (https://qrstudiofree.com)"
---

# Specifications & Print Guide — Engineering Standards & Privacy Manifesto

> Comprehensive documentation covering ISO/IEC 18004 compliance, optical DPI formulas, optimal Reed-Solomon error correction, and zero-telemetry architecture.

## 01 · Privacy Manifesto
### The Privacy Manifesto
QR Studio was engineered with a strict principle: your data belongs exclusively to you. Every QR code generated on this platform is calculated within client-side memory using JavaScript and WebAssembly.

No URLs, passwords, contact cards, or geographic coordinates ever touch our servers. There are no tracking cookies, no surveillance analytics, and no third-party telemetry.

## 02 · Error Correction (ECC) Standards (ISO / IEC 18004)
### Reed-Solomon Error Correction (ECC)
Error correction allows QR codes to be successfully read even if partially obscured, soiled, or damaged. Use Level H (30%) when embedding central logos, and Level M (15%) for dense text data.

- **Level L (Low) — ~7% Data Recovery**: Produces the smallest, least dense grid. Recommended for lengthy plain text or dense data where no logo is used.
- **Level M (Medium) — ~15% Data Recovery**: The industry standard for clean website URLs and digital displays. Offers optimal balance between density and reliability.
- **Level Q (Quartile) — ~25% Data Recovery**: Recommended for industrial environments, curved surfaces (bottles, cans), or outdoor posters subject to weathering.
- **Level H (High) — ~30% Data Recovery**: Mandatory when embedding a logo in the center of the QR code. QR Studio automatically switches to Level H when a logo is attached.

## 03 · Physical Reproduction & Print DPI Standards
### Print Resolution & DPI Standards
For professional offset and digital print, always export vector SVG. When raster PNG is required, generate at 300 DPI or higher using the 4096px export setting to ensure crisp scanning under varying lighting.

1. **Minimum Physical Size**: For close-up scanning (e.g. business cards, flyers), never print smaller than **2cm × 2cm (0.8" × 0.8")**.
2. **Scanning Distance Ratio (10:1)**: As a rule of thumb, the ratio of scanning distance to QR code size should be roughly 10:1. For a billboard scanned from 10 meters away, the QR code should measure at least 1 meter wide.
3. **The Quiet Zone**: Always preserve at least 4 modules (or 8–16px) of blank margin around the perimeter of the QR code.