Send a link, a screenshot or a whole file to the computer next to you.

Yes — that is the point of it existing. Both machines run Webstarted Toolbox and sit on the same local network, and each one sees the other in the list by its machine name. Nothing about the transfer is platform-specific: text arrives as text, an image arrives as a PNG. There is no mobile version, so phone-to-laptop is not what this does.

No, and it would be dishonest to bury that. The content travels in the clear over your local network, which is why the widget says so on the screen where you enable it: use it on networks you trust. What the optional shared code adds is authentication — who is allowed to send to you — not secrecy. If what you are moving would hurt you in the hands of whoever else is on that WiFi, this is the wrong tool for it.

No. Discovery is a broadcast on your own network and the transfer is a direct connection between the two machines, on a single port they both open. There is no account, no relay, no cloud storage and nothing to sign into — which also means the two computers must genuinely be on the same network, not merely both online.

Almost always one of three things. Both machines need the widget open — the ports only exist while you are looking at that tab, so you open the same tab on both. On macOS, Toolbox needs the “Local Network” permission; the widget has a button that opens exactly that pane in System Settings so you can check the box. And the network has to actually pass broadcasts: a guest network with client isolation, two different WiFi bands routed apart, a VPN capturing the traffic, or two subnets will all leave the list empty. Devices announce themselves every few seconds and drop off the list about twelve seconds after they stop.

Yes. Drag a file onto the panel or press “Choose file…”, and anything your machine can read goes across with its bytes and its name untouched: a PDF arrives as that PDF, a JPG arrives as a JPG, a 2 GB video arrives as that video. The ceiling is 4 GiB per file. One file at a time, though: there is no multi-select and no folders, so a folder gets zipped first or sent piece by piece.

Neither, and that is the whole design. The sender hands the app a path, not the contents, and both sides work in 256 KiB chunks straight to and from disk, so memory use stays flat whether the file is 5 MB or 4 GB. It also means the receiving machine is never holding a file it has not agreed to take: the name, the size and who is sending arrive first, and the content only starts moving after you press Accept.

It is checked, not assumed. The sender hashes the file with SHA-256 before sending, the receiver hashes what it writes, and the two have to match. While it is arriving it is a “.wtbx-part” file that is not your file yet; it is renamed to the real name only after the hash checks out, and if anything went wrong the part file is deleted and both sides say so. That is the difference between a failed transfer and a truncated zip that opens and then is not right.

No to both, and both are deliberate for now. There is no resume: on a local network a 4 GiB file is minutes, so a cut transfer is retried rather than repaired. And received files always land in Downloads, the same place images already went. You can cancel from either side at any point, and a transfer that is already running survives hiding the popover, so clicking away mid-send does not kill it.

Text goes to the clipboard of the receiving machine, so the next paste is it. An image is saved to the Downloads folder as a PNG, and it never overwrites: a name already taken gets a numbered one instead, and the widget offers to reveal the file. Neither happens on its own — an incoming item shows up as a card with a preview and two buttons, and until you press Copy or Save nothing has touched your clipboard or your disk.

It is optional, and it decides who may send to you: set one on a machine and only devices carrying the same code can deliver anything to it. Under the hood it is a challenge-response — the receiver issues a fresh random nonce per connection and the sender answers with an HMAC of the code over that nonce, compared in constant time — so a wrong code is refused before a single byte of content is read, and a reply captured once cannot be replayed later. The dice button generates a readable code like ABC-DEF, with I, O and Q left out of the alphabet so nobody mistypes them as 1 or 0 while reading it aloud.

Up to 256 KB of text, 25 MB for an image and 4 GiB for a file. The receiving side does not trust what arrives: it checks the magic bytes, really decodes the image with limits on dimensions and memory so a small file cannot claim to be 30,000 pixels wide and exhaust your RAM, and then re-encodes it to PNG — the sender’s raw bytes are never passed along. The filename is stripped down to a plain name too, with no paths and no invisible characters that make a file display as something it is not.

Because finding the other computer means broadcasting on your network, and macOS gates that. The prompt appears when you press Enable, not when you open the app, which is exactly why the widget starts behind a short explanation instead of asking for a permission out of nowhere. If you dismissed it, the peer list stays empty — and the widget has a button that opens System Settings → Privacy & Security → Local Network so you can turn it back on.

No. The sockets open when you enable the network in the widget and close as soon as you look away — hiding the popover shuts them, and the enable step is not remembered between sessions, so it is always a deliberate click rather than something inherited from last week. The trade is honest: a discoverable machine is only discoverable while you are at it, and in exchange nothing is listening the rest of the day.

Not today, and this widget is deliberately opted out. Toolbox ships a local MCP server that widgets can expose actions to, and this one exposes none — plus it is marked as off for agents, so if actions are ever added they start disabled and need your explicit consent. Sending data off the machine is the one capability where “on by default” is indefensible.

Yes. Webstarted Toolbox is a free beta, needs no account, and this comes built into the app — it is in the Share tab the moment you install it. Desktop only: macOS menu bar and Windows tray.