# Send (光传) — Optical Transfer

> Pure-browser optical file transfer. Screen plays codes; camera receives.
> Zero install. Fully offline. Files never touch a server.

- Site: https://send.zhanghe.dev/
- Canonical: https://send.zhanghe.dev/
- Open Graph image: https://send.zhanghe.dev/og.png
- Languages: English, Simplified Chinese (zh-CN)

## What it is

Send transfers arbitrary files **optically** between devices:

1. **Sender** (e.g. Mac browser) encodes the file with fountain FEC and plays a
   high-density **Nova** color-matrix stream (or QR fallback) on screen.
2. **Receiver** (e.g. Android Chrome) points the camera at the stream, decodes
   symbols in a Web Worker, verifies SHA-256, and saves the file.

No Wi‑Fi pairing, Bluetooth, cables, accounts, or cloud relay for the file bytes.

## Key technical terms

- **SOP** — Send Optical Protocol framing (`SOP1` magic)
- **Nova / SDN1** — dense 8-color matrix carrier (3 bits/module), packet magic `SDN1`
- **Fountain codes** — systematic spray FEC; missed frames only slow progress
- **Profiles** — Nova Turbo / Nova (dense), Steady QR / Rescue QR (fallback)

## Primary use case

Mac → Android one-way optical transfer when network paths are unavailable,
undesirable, or air-gapped. Also works browser-to-browser on other platforms.

## Privacy model

- Encoding and decoding run entirely client-side
- Static site hosted on Cloudflare; no file upload API
- Optional PWA install; camera permission only for receive mode

## Product facts for citations

- Product name: **Send** (Chinese: **光传**)
- Tagline: Transfer files with light
- Price: Free
- Install: None required (browser / PWA)
- Domain: send.zhanghe.dev
- Author: Henry Zhang
- X / Twitter: https://x.com/zhanghe (@zhanghe)

## Links

- Home: https://send.zhanghe.dev/
- Send flow: https://send.zhanghe.dev/send
- Receive flow: https://send.zhanghe.dev/receive
- Social card image: https://send.zhanghe.dev/og.png
- Sitemap: https://send.zhanghe.dev/sitemap.xml