QR Code Generator - Create QR Codes Online

The QR Code (Quick Response Code) is a matrix two-dimensional barcode invented by the Japanese company DENSO WAVE in 1994. Its essence is encoding text, numbers, or binary data into a matrix pattern of black and white squares — white squares represent 0, black squares represent 1, and scanning devices recognize the arrangement of these squares to reconstruct the original data.

The three finder patterns of a QR code are the key to fast recognition: at the top-left, top-right, and bottom-left corners of the QR code, there is a nested square pattern composed of 7×7 modules. The scanner identifies these three "targets" to quickly determine the position, orientation, and tilt angle of the QR code. This is why QR codes support 360-degree rotation recognition.

QR codes support four encoding modes: Numeric mode stores only digits 0-9, with the highest efficiency; Alphanumeric mode supports 0-9, A-Z, and 9 special symbols; Byte mode stores ISO-8859-1 characters, suitable for plain text; Kanji mode is optimized for Japanese text storage. This tool uses Byte mode with UTF-8 encoding to support complete Chinese and English content.

The version of a QR code ranges from 1 to 40. For each increase in version, the number of modules per side increases by 4. Version 1 has 21×21 modules, and Version 40 has 177×177 modules. The larger the version, the more data can be stored, but the larger the physical size of the QR code. This tool automatically selects the smallest available version based on the length of your input content, ensuring the smallest QR code size while meeting storage requirements.

One of the most powerful features of QR codes is the Reed-Solomon error correction algorithm, which allows QR codes to be correctly recognized even when partially damaged or obscured. This is why we can place logos in the center of QR codes or print them on product packaging that may wear out.

Error correction levels are divided into four grades — the higher the level, the more redundant data, and the stronger the damage resistance:

• L (Low): approximately 7% of data recoverable — suitable for clean, flat printing scenarios, such as electronic tickets and posters. It has the lowest error correction capability but can store more data in the same version.
• M (Medium): approximately 15% of data recoverable — the most commonly used default level, balancing error correction capability and data density. Suitable for most common scenarios, such as business cards, menus, and general marketing materials.
• Q (Quartile): approximately 25% of data recoverable — suitable for harsher environments, such as outdoor advertisements, industrial labels, and logistics packaging.
• H (High): approximately 30% of data recoverable — the highest error correction level. When you need to add a logo or icon in the center of a QR code, it is strongly recommended to choose level H, because the logo will cover approximately 15%-20% of the module area.

A practical tip: use level H error correction when adding a logo. After uploading a logo, the tool will automatically switch to level H (if not already set). In addition, the quiet zone around the QR code is also important — maintain at least 4 modules of white margin, which can significantly improve scan recognition rates, especially in complex backgrounds or rapid close-range scanning scenarios.

About colors and contrast: traditional QR codes use black and white color schemes, ensuring the highest recognition contrast. However, in practice, QR codes only require sufficient brightness contrast between modules — dark colored modules with a light colored background can usually be recognized. It is recommended that the contrast between foreground and background colors be no less than 60%, avoiding low-contrast or similar color schemes.

This tool uses a fully localized QR code generation scheme — all input text, URLs, WiFi configurations and other content are not uploaded to any server. All calculations are performed in your own browser through JavaScript. When you click "Generate QR Code" on your local device, everything from text encoding and Reed-Solomon error correction calculations to the final PNG/SVG image rendering is completed entirely in browser memory.

Why is this important? When generating QR codes containing sensitive information (such as WiFi passwords, personal contact information, internal system links), you do not want this information to be uploaded to third-party servers or recorded. A fully localized approach means: even when disconnected from the internet, the tool still works normally; after closing the browser tab, all input data is immediately cleared from memory; the generated QR code image file never appears in any network location before you download it.

For scenarios involving highly sensitive information (such as internal system access addresses, account credentials, personal contact information), we still recommend closing the browser tab after completing operations to avoid accidental leakage through browser auto-fill or session recovery.

For more details on this tool's privacy protection strategy, see our Privacy Policy page.