How Peerxfer works

Peerxfer sends a file or folder directly between two browsers without uploading it to cloud storage. There is no sign-up, no install and no file size limit built in; only both sides’ internet connections and free disk space set the limit.

Step by step

1. Choose the file or folder. Use “Choose file” or “Choose folder” on the home page, or drag and drop. Your files never leave your browser.
2. Set a password. Peerxfer generates a random 10-character password for you (xxxxx-xxxxx). You can type your own instead.
3. Share the link and the password. Click “Create share link”. Send the link (or the QR code) and the password to the receiver, ideally through two different channels. Keep this tab open until the transfer finishes.
4. The receiver connects. They open the link, enter the password and choose where to save the file. The transfer starts.
5. Done. Both sides see a “Transfer complete” notice. To send another file, press “Start a new transfer”; each transfer uses a new link and password.

What happens behind the scenes

Peerxfer uses WebRTC to open a direct data path between browsers. The Peerxfer server only relays small “handshake” messages so the two sides can find each other (signaling). File bytes never pass through the server and are not stored anywhere.

• Encryption: the WebRTC data channel is encrypted with DTLS. On top of that, both sides verify each other with a key derived from the password, so someone who does not know the password cannot get in the middle.
• The password is never sent to the server. It is processed in your browser with PBKDF2; only a derived room key reaches the server.
• Integrity: the file is split into 8 MiB batches and each batch is verified with SHA-256. Corrupted data is not written to disk.
• Resilience: if the connection drops, both sides reconnect automatically for up to 10 minutes and continue from the last verified point.

Very large files

For files of 10 GB and more, Peerxfer automatically uses part-by-part saving on the receiving side: the file is written to disk in 256 MiB parts and can resume with the same link, password and folder even if the tab is closed. Merging the parts needs extra free space equal to the file size.

Limits

• Sender and receiver must be online at the same time; Peerxfer does not store files for later download.
• A direct connection can fail on very restrictive corporate networks.
• Receiving a folder needs desktop Chrome or Edge; empty folders are not sent.

Have questions? Read the FAQ or contact us.

Send a file now →

Also read

• FAQ
• Send large files
• PC to phone
• Share without the cloud

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