A live clipboard, synced in realtime

What makes a clipboard live

The test is whether anything has to be pressed. A conventional online clipboard gives you a box, you paste into it, you press Send, and the other device shows the result once it reloads or polls. Every step is a decision, and the round trip is long enough that people stop trusting it and go back to messaging themselves.

A live clipboard removes all three steps:

• Nothing to press. Keystrokes stream to the other device while you are still typing.
• Nothing to reload. The connection stays open, so arriving text lands on its own.
• Nothing to paste into. At the top setting, copying anywhere on the machine is enough — the clipboard itself is what is being watched.

The last one is the real prize and the one worth being careful about, because a clipboard that syncs everything syncs the passwords you copied for unrelated reasons too. That is why it is a rung you climb to rather than the only way it works.

Live clipboard, realtime clipboard, online clipboard

These are three names for the same category, and the differences are in emphasis rather than in kind. People searching for any of them usually want the same thing, but the words do carry different expectations and it is worth saying which is which.

The last row is the one that trips people up. Cloud clipboard is Microsoft's and Apple's name for the feature built into their own operating systems, and both are locked to one ecosystem and one signed-in account: Windows clipboard history syncs between Windows PCs, Universal Clipboard between Apple devices, and neither crosses to the other. If you are searching because your phone and your laptop are from different makers, the built-in cloud clipboard is the thing that cannot help you.

Realtime typing, not just realtime pasting

There are two separate things a clipboard can do in realtime, and most tools that claim the word only do the second. Delivering a finished clip quickly is the easy half. Showing the text while it is still being written is the half that makes a shared clipboard feel like one surface rather than two.

Here, typing is streamed and clips are committed, and they are deliberately different paths:

1. While you type, the editor sends the text about ten times a second. The far side renders it and does nothing else with it — no history entry, no clipboard write.
2. When you stop, after 800 ms of quiet, or on blur, or on Ctrl+Enter, it commits. That is the moment it becomes a real clip: it enters history, and at the top rung it goes to the system clipboard.

Streaming stops above roughly 4 KB and the text syncs on commit only, which in practice is invisible — text that long is pasted, not typed.

Two people typing at once is never merged. Merging concurrent edits needs a CRDT, and this is a clipboard, not a document editor. An incoming stream is dropped while you are typing, and an incoming clip that would overwrite unsaved work is offered rather than applied. What prevents the collision in practice is seeing it coming: each peer's caret tints their line in the gutter, in their own colour, so you watch the other person start before you both commit.

How far live sync reaches

The reach of sync is one setting with three rungs, and each adds exactly one thing to the one below it. It sits in the app header rather than in a settings menu, because it is the control that decides what leaves the machine.

App is the rung most people should sit on for shared or work machines: the session is fully live, but your operating system's clipboard is neither read nor written, so nothing you copy for an unrelated reason ever leaves. Clipboard is the one that makes copying anywhere on the machine enough, and it is a single setting governing both directions — a device that has stopped sending is not quietly still receiving.

What live sync actually costs

Reading the system clipboard automatically is a browser capability, not a feature a website can simply decide to have, and the constraints are worth knowing before you conclude something is broken.

• Automatic capture needs a Chromium-based browser — Chrome, Edge, Brave, Opera. Firefox and Safari can send and receive text you paste in, but cannot read the clipboard themselves.
• No browser reads the clipboard while its tab is in the background. That is a browser security rule and it applies to every web-based tool in this category, not just this one. The window has to have focus.
• A clip is capped at 24,000 characters, which is the relay's frame size after encryption rather than an arbitrary limit.
• Files are not text and do not stream — they go directly between browsers over WebRTC, up to 5 MB each.

If sync is not arriving at all, the causes are nearly always one of a short list — clipboard sync not working walks through them in order.

Using a live clipboard

RealtimeClipboard is a live clipboard of the shared-key kind, so there is nothing to sign up for:

1. Open the app on both devices.
2. Type the same short key on each. That key is what pairs them — no account, no email, no login.
3. Type. It appears on the other screen as you go.

The key never leaves your browser: what reaches the relay is SHA-256(key), used only as a room address, plus text already encrypted with AES-GCM. The relay forwards ciphertext between connections and stores nothing on disk, so "live" here does not mean "held on a server for you to collect" — there is no copy anywhere to collect. It works across different networks, not only on the same Wi-Fi, which is the line most local-only tools like Snapdrop stop at.

Open a live clipboard