Security: how Send keeps your files private
Send was built so that the people running it can't see what you send, even if they wanted to. Here is exactly what protects you, and the limits you should know.
What protects you
| Protection | What it means for you |
|---|---|
| End-to-end encryption (WebRTC DTLS) | Files and notes are encrypted on your device and decrypted only on the other device. Browsers make this compulsory. |
| No upload, no storage | There is no server that holds your file. Nothing can leak from a server that never had it. |
| One-time codes | Codes are 8 random characters from a 32-character alphabet (over a trillion combinations), made by your browser's secure random generator. After pairing, both devices leave the pairing service and the code dies. |
| Accept before anything arrives | The receiver sees the name, type and size of each file and must tap Accept. Nothing downloads or opens by itself. |
| Safety code | Both screens show four pictures computed from the encryption keys of this connection. Same pictures on both = nobody in the middle. |
| Risky-file warning | Programs and scripts (.exe, .msi, .apk, .bat, .ps1, .js, macro documents and more) get a clear warning before you accept. |
| Locked-down page | The transfer page may only run its own code plus two pinned libraries (PeerJS and a QR-code drawer, each checked against a fixed fingerprint so a changed copy is refused). It shows no ads and loads no trackers. |
| Code kept out of addresses sent to servers | Pairing links put the code after a # sign. Browsers never send that part to any website. |
Honest limits
- The other device sees your internet address. Every direct connection works this way (video calls too). It shows roughly which city or network you are on, not who you are.
- Only accept files from people you know. Encryption protects a file on its way; it can't make a harmful file safe. Never run a program someone unexpected sent you.
- The pairing service runs on Cloudflare's network. It sees that two devices connected, and their network addresses, for the moment it introduces them. It keeps no record of them. It never sees files or notes, and the safety code lets you confirm it didn't place itself in the middle.
- A device that is already infected (malware, a screen-recording app) can see whatever you see. Send can't protect a compromised device.
Good habits
- Read the code out loud or scan the QR code rather than posting it publicly.
- For something sensitive, compare the safety code on both screens before sending.
- Tap Disconnect when you are done.
Found a security problem? Please tell us through the contact page.