QR Metadata Viewer

QR metadata refers to the technical parameters encoded within a QR code beyond the decoded content: version (1-40), error correction level (L/M/Q/H), mask pattern (0-7), format information bits, alignment pattern positions, and Reed-Solomon codeword structure. This metadata is useful for developers validating QR generators, quality assurance teams auditing printed codes, and advanced users troubleshooting scanning failures.

The EC level is extracted from the format information embedded in the QR code. The tool reads the 15-bit format info codeword from pixel data around the finder patterns, XORs it with the format info mask pattern (0x5412), applies BCH error correction to fix up to 3 bit errors, and decodes the 5 data bits: bits 4-3 encode the EC level (01=L, 00=M, 11=Q, 10=H) and bits 2-0 encode the mask pattern reference.

A mask pattern (0-7) is a mathematical transformation applied to the QR code modules to balance dark and light areas for reliable scanning. Different masks work better on different surfaces — for example, mask patterns with vertical stripes may perform poorly on printed surfaces with similar textures. The tool shows which mask pattern was used in the QR code you uploaded.

Format information is a 15-bit codeword stored in two redundant copies around the finder patterns. It encodes the error correction level (2 bits), mask pattern reference (3 bits), and 10 Reed-Solomon BCH error correction bits. The two copies allow the decoder to correct up to 3 bit errors, ensuring reliable EC level and mask pattern detection even in damaged codes.

The version number (1-40) is directly decoded by the jsQR library from the QR code's structure. Version 1 has 21×21 modules, and each subsequent version adds 4 modules per side, up to version 40 with 177×177 modules. Versions 7 and above also include version information blocks for additional error correction of the version number itself.

Alignment patterns are 5×5 module squares placed at fixed positions within larger QR codes (version 2 and above). They help the scanner correct geometric distortion when scanning at an angle. The number and position of alignment patterns depends on the version — version 2 has 1 alignment pattern, while version 40 has 49 alignment patterns arranged in a 7×7 grid.

QR codes use Reed-Solomon error correction, which divides the data into blocks and adds parity codewords to each block. The EC level determines the ratio of data codewords to error correction codewords. For version 6 with EC level L: 136 data codewords + 36 EC codewords (blocks: 2 blocks × 68 data codewords each). At EC level H: 60 data codewords + 112 EC codewords (4 blocks × 15 data codewords each). More EC codewords mean higher resilience but lower data capacity.

Yes. The tool attempts to decode the QR code in both standard and inverted modes. If the initial decode fails, the image is binarized (converted to pure black and white) and re-decoded with inversion enabled. The result card indicates whether the code was decoded in standard or inverted mode.

The BCH error correction can correct up to 3 bit errors out of the 15-bit format info codeword. The confidence percentage reflects how many bit errors were corrected — 100% means no errors detected, 93% means 1 bit was corrected, 87% means 2 bits, and 80% means 3 bits. If more than 3 errors exist, the tool cannot reliably decode the format info and falls back to a default EC level (M) with a reduced confidence display.

Module size is calculated by measuring the pixel distance between the top-left and top-right finder pattern centers and dividing by the number of modules between them (10 + 4 × version). Finder pattern distances are measured as straight-line Euclidean pixel distances between the three finder pattern center coordinates returned by jsQR. These measurements help assess whether the QR code is skewed or has adequate size for scanning.

Yes. The tool supports versions 1 through 40 with complete lookup tables for total codewords and data codewords at all four EC levels. Alignment pattern positions are also included for all versions, and the overlay draws alignment pattern markers for version 2 and above.

Absolutely. Developers can use QR Metadata Viewer to verify that their QR generator produces correct metadata: confirm the expected EC level, check that the mask pattern selection is appropriate, verify the version selection is correct for the data length, and inspect the raw binary output for any encoding anomalies.

Images up to 20 MB are accepted in PNG, JPEG, WebP, GIF, and BMP formats. Images larger than 4096 pixels in any dimension are automatically scaled down for processing. For best results, ensure the QR code occupies a significant portion of the image frame and the resolution is at least 300×300 pixels.

No. All processing — image decoding, QR detection, format info extraction, and metadata computation — happens entirely in your browser using client-side JavaScript and the jsQR library. Your images and decoded data never leave your device. This makes the tool suitable for analyzing proprietary designs, confidential documents, and sensitive payment QR codes.