NMT Code

English | 한국어

NMT Code (needmoretruth code) is a two-dimensional code for the cameras of current phones and computers. The same content needs fewer modules than a QR Code.

The NMT Code symbol at the bottom holds https://github.com/needmoretruth/nmtcode. The QR Code above it holds the same address, so a phone that reads only QR Codes gets a link to this page. --qr adds that QR Code; printed codes (--profile print) have it by default.

Version 0.0.1 makes black-and-white codes as PNG or SVG, and reads them from camera photos, screenshots and image files (PNG, JPEG). It comes as a command-line tool, a web page and a Rust library. Colour codes and file transfer over several codes are still being built. Codes made with 0.0.1 stay readable by every later 0.x version.

Size compared with QR Code

Content	Bytes	NMT Code	QR Code
https://github.com/needmoretruth/nmtcode	40	20 × 28 = 560	29 × 29 = 841
A Korean sentence, 84 bytes in UTF-8	84	24 × 36 = 864	37 × 37 = 1,369 (UTF-8) · 33 × 33 = 1,089 (EUC-KR)
An 87-byte English sentence	87	24 × 36 = 864	37 × 37 = 1,369
50 digits	50	20 × 28 = 560	25 × 25 = 625

• Both codes use their lowest error-correction level, which restores about 7.5% (NMT Code) and 7% (QR Code) of the bytes. QR Code is the smallest version that holds the content. Many QR readers decode Korean correctly only in UTF-8.
• The counts leave out the quiet zone: NMT Code needs 2 modules on each side, QR Code 4.
• NMT Code symbols are rectangles whose sides are within a factor of 2, which is why they are not square.
• The counts are for the symbol alone. With the QR Code of --qr beside it, the image is larger than a QR Code of the same content.
• Measured on 2026-09-29 with nmtcode 0.0.1, zxing-cpp 3.1.1 and segno 1.6.6.

Reading camera photos

On synthetic camera photos (1920 × 1080, 3 camera pixels per module, blur of half a module, noise at 30 dB, JPEG quality 80, a tilt of up to 30°, any rotation, a cluttered background), 992 of 1,000 codes were read and none was read wrongly. Reading one photo took 11.9 ms (median) on a desktop processor (AMD Ryzen 5 7500F).

• At a tilt of 45° with blur of half a module, 32–53% of the photos were read; with blur of 0.7 module, at most 58%. No photo was read wrongly in any condition.
• Photos from real phones are not measured yet.
• cargo run -p nmtcode-sim --release --example measure repeats the measurement.

Install

Download the file for your system from the latest release:

System	File
Linux, x86_64	nmtcode-<version>-x86_64-unknown-linux-musl.tar.gz
Linux, ARM64	nmtcode-<version>-aarch64-unknown-linux-musl.tar.gz
macOS, Apple silicon	nmtcode-<version>-aarch64-apple-darwin.tar.gz
macOS, Intel	nmtcode-<version>-x86_64-apple-darwin.tar.gz
Windows, x86_64	nmtcode-<version>-x86_64-pc-windows-msvc.zip

Unpack it and put nmtcode (nmtcode.exe on Windows) on your PATH. SHA256SUMS in the release lists the checksum of every file. The macOS binaries are not signed, so macOS asks you to allow them the first time.

To build from source instead, install Rust and run:

git clone https://github.com/needmoretruth/nmtcode.git
cd nmtcode
cargo install --path crates/nmtcode-cli --locked
nmtcode --version

The repository pins Rust 1.98.1, and rustup installs it on the first build.

Use the command

nmtcode make --url https://example.com -o link.png
nmtcode make --text "Meet at the north entrance at 7 pm" -o note.svg
nmtcode make --file report.pdf -o report.png
nmtcode make --profile print --dpi 600 --text "Printed label" -o label.png

nmtcode read photo.jpg
nmtcode read report.png --out received/
nmtcode read link.png --json

• make writes PNG or SVG by the file extension. --level 0-3 sets error correction, and --size WxH, --max-width and --max-height set the size in modules.
• read takes a PNG or JPEG: a camera photo, a screenshot or a file from make. It prints text and URLs, and never opens a URL. Files are saved only with --out, never over an existing file, and under a name stripped of directories.
• nmtcode make --help and nmtcode read --help list every option.

Use the web page

The release has nmtcode-web-<version>.zip, a page that makes codes and reads them with the camera or from an image file. Everything runs in the browser, and nothing you type or photograph leaves the device.

unzip nmtcode-web-0.0.1.zip
cd nmtcode-web-0.0.1
python3 -m http.server 8000

Open http://localhost:8000. Browsers turn on the camera only for https:// pages and localhost; reading an image file works from any address.

Use the library

use nmtcode::{DecodeOptions, EncodeOptions};
use nmtcode_detect::DetectOptions;
use nmtcode_render::RenderOptions;

let url = "https://github.com/needmoretruth/nmtcode";
let symbol = nmtcode::encode_url(url, &EncodeOptions::default())?;
let png = nmtcode_render::render_png(symbol.grid(), &RenderOptions::default())?;

// Any PNG or JPEG: a camera photo, a screenshot, or the PNG above.
let image = nmtcode_detect::read_image(&png)?;
for found in nmtcode_detect::find(&image, &DetectOptions::default()).found {
    let decoded =
        nmtcode::decode_with_erasures(&found.grid, &found.uncertain, &DecodeOptions::default())?;
    println!("{}", decoded.records[0].text().unwrap_or("(binary record)"));
}

The full program is crates/nmtcode-cli/examples/round_trip.rs. The crates are not on crates.io yet; depend on them by Git URL.

Crate	What it does	no_std
nmtcode	Encode records to a module grid and decode them back, with erasures from the detector
nmtcode-core	Module grid, format word, container, records, CRC-32C, reader errors	✅
nmtcode-ecc	Reed-Solomon error correction over GF(2^8)	✅
nmtcode-payload	Codecs: stored, digits, alphanumeric, token table, Hangul packing, brotli	✅ without brotli
nmtcode-symbol	Finder patterns, reference marks, module placement, whitening	✅
nmtcode-render	PNG and SVG output, with or without a QR Code beside the symbol
nmtcode-detect	Finds symbols in camera photos, screenshots and image files (PNG, JPEG)
nmtcode-cli	The nmtcode command
nmtcode-wasm	The WebAssembly module of the web page
nmtcode-sim	Synthetic camera photos for tests and measurement (not published)

The no_std crates also build for wasm32-unknown-unknown. No crate uses unsafe.

Specification

The format is written in spec/, version 0.2. It defines every bit, so another program can make and read NMT Code without this code. The worked examples of the specification and its complete test symbols (Annex A) are tests of this repository.

Check

scripts/check.sh

It runs formatting, clippy, every test, the wasm32 builds, a check that no crate version reaches 1.0.0, the licences of every dependency, and a check of the files the repository may hold.

Contribute

Pull requests are welcome. Each needs one line agreeing to the Contributor License Agreement (한국어 설명); the pull request template says where. Report security problems privately, as SECURITY.md describes.

License

• Code: MIT or Apache-2.0, at your choice.
• Specification (spec/): CC BY 4.0. CC BY 4.0 grants no patent rights.

QR Code is a registered trademark of DENSO WAVE INCORPORATED.