QR Code Generator

About the QR Code Generator

QR codes (Quick Response codes) are two-dimensional barcodes invented by Denso Wave in 1994 for tracking automotive parts. They are standardized under ISO/IEC 18004 and encode data as a grid of dark and light modules — up to 177 by 177 at version 40 — that a phone camera can decode in milliseconds. Unlike the original linear barcodes, QR codes pack 200 times the data density into the same physical area.

Every QR code carries four error-correction levels defined by Reed-Solomon coding: L recovers 7% of damaged modules, M recovers 15%, Q recovers 25%, and H recovers 30%. Higher levels mean more redundant data and a denser pattern. Choose H for printed materials that may be smudged or partially obscured; choose L for digital displays where every pixel counts.

The QR specification supports four encoding modes that pack different densities: numeric (3.3 bits per module), alphanumeric (5.5 bits), byte (8 bits), and Kanji (13 bits). A version 40 QR at level L holds up to 7,089 numeric digits, 4,296 alphanumeric characters, 2,953 bytes, or 1,817 Kanji characters — enough for a small vCard, a long URL with UTM parameters, or a complete Wi-Fi configuration.

How It Works

This tool builds a request to the public api.qrserver.com endpoint, which renders the QR server-side using a libqrencode backend. The request URL is structured as https://api.qrserver.com/v1/create-qr-code/?size=256x256&ecc=M&data=... with the data URL-encoded per RFC 3986. The server returns a PNG (or SVG when format=svg is set) which the browser loads directly.

The size parameter controls the rendered image’s pixel dimensions, not the QR’s capacity. A larger canvas makes the code easier to scan from a distance or when printed at small physical sizes; the underlying data capacity is determined by the version (1–40) and the error-correction level selected by the encoder.

Error correction uses Reed-Solomon codes over GF(256), the same family of codes used on CDs, Blu-ray discs, and QRAM. The encoder computes parity symbols for each block of data modules and interleaves them so a localized tear or smudge distributes across multiple codewords — this is why a coffee-stained QR still scans.

For URL encoding, the QR specification recommends the ‘alphanumeric’ mode for URLs that contain only 0–9 A–Z $ % * + – . / : because it packs 5.5 bits per module instead of the 8 bits per module required for full byte mode. Most encoders select mode automatically based on the input.

Worked Examples

Encode the URL https://ht99.icu at 256×256 with ECC level M. The output PNG is a 21×21-module QR (version 1) padded to 256 pixels. Even at small print sizes the code remains scannable because the URL is short.

Encode a Wi-Fi configuration WIFI:T:WPA;S:HomeNetwork;P:Sup3rSecret!;; at 512×512 with ECC level H. Phones running iOS 11+ and Android 10+ recognize this format and offer a one-tap join dialog when the camera focuses on the code. The semicolon-separated schema is documented in the Android Wi-Fi QR format spec.

Encode a vCard (BEGIN:VCARD ... END:VCARD) with full contact details at 1024×1024 with ECC Q. The QR fills version 12 or 13 (around 65×65 modules) and remains readable even when printed at 3 cm wide. Avoid ECC L for vCards — one coffee ring will make the contact unreachable.

When to Use This Tool

• Restaurant menus and contactless ordering displayed on table tents.
• Wi-Fi credentials sharing via the WIFI:T:WPA;S:...;P:...;; schema recognized by iOS and Android.
• vCard business cards that auto-import into the recipient’s contacts app.
• Event ticketing and boarding passes where the QR encodes a signed token.
• Payment addresses (BIP-21 Bitcoin, EIP-681 Ethereum, UPI IDs) scanned by mobile wallets.
• App-store deep links that route users to the right platform (iOS App Store or Android Play Store).
• Two-factor-authentication TOTP seeds encoded as otpauth://totp/... per RFC 6238.

Limitations & Disclaimer

This tool renders QR codes via the public api.qrserver.com endpoint, which means the data you encode is transmitted to a third-party server. Do not use it for passwords, payment details, or other sensitive content; for those use cases, run a local library such as qrcode (Node) or qrcodegen (browser). Capacity figures assume an ideal encoder; very long alphanumeric inputs may force byte-mode encoding and reduce capacity by roughly 30%. The error-correction percentages are theoretical maxima; partial obstruction across multiple codeword blocks can defeat even ECC H. See our disclaimer for full terms.

Frequently Asked Questions

Last updated: September 9, 2026  ·  Author: HT99 Tools Editorial Team