cd

What it is

cd is for sending a file to another person without uploading it to a file-hosting service first. The sender opens the app, chooses files, and shares a short receive code or QR link. The receiver joins from a browser and accepts the transfer.

The actual file contents move directly between the two browsers through a WebRTC data channel. The hosted service is used to load the app and help the peers find each other; it is not intended to store the transferred files.

Quick start

Open the cd website.
Choose one or more files.
Copy the receive code or show the QR code to the other person.
Keep both tabs open and visible until the transfer completes.
The receiver saves the file when the browser offers it.

For a reliable handoff, keep both devices awake, use a stable network, and do not close or refresh either tab during the transfer.

What happens under the hood

sender browser ── WebRTC data channel ── receiver browser
       \              /
        signaling / session setup
             hosted Worker

The signaling step exchanges the information needed to establish the peer connection. Once connected, file data uses the browser's WebRTC data channel. This means large transfers are usually limited by the slower device, browser memory, network path, and WebRTC behavior rather than a server-side file quota.

Tech stack

Part	Technology	Job
Frontend	Browser JavaScript/HTML/CSS	File picker, code/QR UI, transfer progress
Peer connection	WebRTC data channels	Direct browser-to-browser file transfer
Signaling	Worker-hosted signaling service	Helps peers negotiate a connection
Deployment	Cloudflare Workers	Hosts the app and signaling endpoint
Repository language	Go plus web assets	Current repo implementation and tooling

Privacy and limits

The app does not intentionally persist the file contents on the hosted service. It is still a browser application: the two people involved can see and save the files, and the network/browser environment can affect the connection. This is not an encrypted archive or an access-control system for highly sensitive material.

Both browsers must stay connected. Some restrictive corporate networks, VPNs, or browser policies can interfere with WebRTC. Very large files can also run into memory or browser download limitations.

Troubleshooting

The code does not connect: refresh both sides and create a new transfer. Disable a VPN temporarily and try a normal network. Corporate or guest networks may restrict peer connections.

The QR code is not working: copy the text code manually. The receiver can open the website on any modern browser and enter the code.

The transfer stops halfway: prevent sleep, keep both tabs open, and retry with a stable connection. For very large files, split the archive or use a local network transfer tool.

The receiver cannot save: check browser download permissions and available disk space.

Self-hosting and development

git clone https://github.com/YashasVM/cd.git
cd cd

The repository README and deployment configuration are the source of truth for the current Worker commands and environment values. Inspect the signaling path before deploying a public instance, and never put secrets in browser-delivered code.

cd