1. Put both devices on the same public route
Open CopyPaster on the sending and receiving devices. They do not necessarily need the same local Wi-Fi address, but their requests must reach the service through the same public IP address. Two devices on the same home router usually satisfy this condition. A phone using cellular data and a laptop using Wi-Fi usually do not.
VPNs, corporate proxies, mobile carrier gateways, and privacy relays can change the visible public route. If only one device uses a VPN, disconnect it or connect both devices through the same VPN exit before trying again.
2. Compare the room keys
Each browser displays a room key near the top of the workspace. Compare the full visible key on both devices before entering content. Matching keys mean the service assigned both requests to the same room. Different keys mean the browsers cannot synchronize with each other in their current network configuration.
Do not use the presence of a matching key as proof of identity. The key describes the room, not the person viewing it. Another user behind the same public address may receive the same room.
3. Choose Text, Files, or Chat
Use Text for URLs, notes, code fragments, addresses, and other plain text. It is the fastest option and accepts up to 20,000 characters. Wait until the receiving browser shows the complete text before copying it.
Use Files for supported PNG, JPG, WEBP, PDF, TXT, or DOCX files up to 10 MB. Confirm the filename and size before uploading, then download the file on the other device. Uploaded files are temporary and configured to expire after one hour.
Use Chat for a short back-and-forth exchange during troubleshooting or a handoff. Chat is not intended as a permanent conversation history.
4. Verify the received material
On the receiving device, check that text is complete and that a downloaded file opens correctly. For important non-sensitive documents, compare the filename and file size with the sender. Do not assume a partial upload or interrupted download will repair itself later.
If updates stop appearing, check the connection indicator, reload both browsers, and compare the room keys again. A network handoff can change a phone from Wi-Fi to cellular data and silently move it to a different room.
5. Clear the room after the transfer
Copy the text or save the file on the receiving device before clearing anything. Then clear shared text, clear chat messages, and remove uploaded files. Early cleanup reduces the time during which another device on the same public route could encounter the material.
Material that should use another service
Use an authenticated, encrypted service for passwords, one-time codes, private keys, financial records, medical information, identity documents, confidential work files, or anything that would cause harm if another network user saw it.