Persistent Room: One Code, and Sync Only the New Files

The problem with a new code every time

SharingCast normally creates a fresh random code, such as SC-7K2QF, every time you start sharing. That is ideal for one-off transfers: the code is only useful for a few minutes and then it is gone.

But many people send files between the same devices again and again. A designer who moves files from their phone to their work PC every day, an office where one machine shares scanned documents, or a teacher who sends material from the same laptop to the classroom computer. For them, reading out a new code every time is a chore. And when the same files stay on offer, the receiving device should not have to download them all over again just to get the one new file that was added.

What a Persistent Room is

A Persistent Room is a room with a code that never changes. You open it in the Room tab, under My room, on the device that keeps the files. That device is the host of the room. SharingCast remembers the room’s files on that device, so after you close and reopen it, the room opens again with the same files until you remove them.

The room has its own connection. While it is open, the Send tab stays free, so you can still send a one-off file to someone else with a normal random code, without closing your room.

The other devices open their Room tab and choose Join a room. They join once, with the code and password. From then on, the files that device has not saved before are listed as new, and they tick the ones they want and tap Download selected. Nobody gets the same file twice by accident, and nothing downloads unless you choose it.

How to open your room (host device)

1. On the device that will keep the files, open sharingcast.com (or the Windows or Android app) and tap the Room tab, then My room.
2. Add the files or folders you want to keep in the room. Tap the box to choose them, or drag and drop them anywhere on My room. Use the × next to a file to take it out, or Remove all to empty the room.
3. Choose the room code. The box already shows SC-, so type five letters or numbers you will remember, for example DESKA for SC-DESKA. A random code is filled in if you just want to start.
4. Set a password (see below). The room remembers it, so you do not have to type it again after a restart.
5. Tap Start room. Share the code and password with the people who need them, or use Copy room link or the QR code.

Whenever you add files to the room, every device that is already joined sees them straight away as new files waiting to be synced. Tap Stop room to close it; the files stay in My room until you remove them. Clearing the browser’s site data on the host device removes the saved room and its files, so set it up again if that happens.

How to join and Sync (receiving device)

1. Open sharingcast.com (or the app), tap the Room tab, then Join a room. If someone sent you a room link, opening it takes you straight there with the code filled in.
2. Enter the room code (the box already shows SC-, so type the five characters after it) and the password, then tap Join room. You only do this once on each device; the room is remembered and reconnects by itself next time.
3. When the host has files you don’t have yet, the Room tab shows a number, the button reads, for example, Sync (3 new), and the new files are listed with a tick next to each. When the host adds more files, they appear in the list by themselves. Tap Sync at any time to check again.
4. Untick anything you don’t need, then tap Download selected. Only the files you chose are transferred.
5. Tap Download next to a file to save it, or Download all · ZIP to save everything that arrived in one ZIP. Saved files are marked Saved ✓.

Need an older file again? Tap Show all files in this room, tick the ones you want, and download them again. To stop using the room on a device, tap Leave room.

The Room tab has its own connection. While a room is joined, the normal Receive tab stays free, so someone else can still send you a one-off file with a regular code at the same time.

How Sync decides what is new

Each receiving device keeps its own short list of files it has saved from that room, using each file’s name, size and date. The list lives in that device’s browser or app, not on a server.

• A file counts as saved only after you tap Download or Download all · ZIP. If a file arrived but you never saved it, the next Sync offers it again, so you cannot lose it by closing the page too early.
• If the host replaces a file with a newer version (a different size or date), Sync treats it as a new file.
• Every receiving device keeps its own list. Five office PCs can join the same room, and each one gets exactly what it is missing.
• Clearing the site data on a receiving device clears its list, so the next Sync offers every file in the room again.

Always add a password

A room code that never changes is convenient precisely because it stays the same. That also makes it predictable: anyone who has ever seen it, overheard it, or read it on a sticky note knows it too. A password closes that gap.

Good practice for passwords on a Persistent Room:

• Use something longer than a few characters, and avoid the company name or the code itself.
• Change it when someone leaves the team. Receiving devices then need to leave the room and join again with the new password.
• Do not write the password next to the code.

One room, one host

A Persistent Room can be hosted from one place at a time. If the same code is turned on in two places, for example in the Windows app and in a browser tab on the same PC, the second one does not take the room away. It waits for about a minute in case the first one is just restarting. If the room is still busy after that, it stops and shows a message that the room is already open in another window, app or device.

To move the room, tap Stop room where it is running (or close it there), then tap Start room on the device you want to host it from. Opening the room’s code or link on other devices to receive is always fine; any number of devices can join and sync.

Good uses for a Persistent Room

• Your own devices. Keep a Persistent Room on your work PC, and your phone and laptop simply tap Sync to pick up whatever you added since last time.
• A shared scanning or download station. One office computer adds scanned documents or reports throughout the day, and each colleague syncs only the new ones.
• A presentation or classroom laptop. The same laptop shares slides, handouts or videos with meeting room or classroom PCs, which sync before each session.
• A small studio. An editing workstation keeps exported files in a room, and the review machine syncs new exports as they appear.

For one-off transfers to people outside your team, a fresh random code from the Send tab is still the safer choice.

Choosing and managing rooms in a team

If several devices in an office host rooms, a simple naming pattern prevents mix-ups. Use the room or desk name (SC-RECEP, SC-STUD1, SC-MEET2), keep a short list of which code belongs to which host device, and review it when equipment changes. Because rooms live in each host device’s browser or app, replacing a computer means setting the room up again on the new one.

It also helps to agree on a simple rule: Persistent Rooms are for internal, routine transfers between known devices; anything sensitive or external uses a fresh code and a fresh password.

What a Persistent Room cannot do

• The host must be online. SharingCast sends files directly between devices and does not keep a copy on a server. Sync works only while the host device is on, connected, and sharing the room. If it is offline, the Room tab says so and keeps trying.
• Sync is one way. Files go from the host to the receiving devices. To send something back, use the normal Send and Receive tabs.
• One room per device. Each device can host one room at a time. Any number of devices can join it and sync, even at the same moment.
• Browsers close when you close them. A browser tab cannot keep a room running after it is closed. For an always-on host, use the Windows or Android app and keep it running.

Frequently asked questions

Is this the same as the old static room code?

Yes, with more features. A saved static code automatically became a Persistent Room with the same code. What is new is the Room tab with Sync on the receiving side, so devices only download what they are missing.

Can several devices join the same room?

Yes. Any number of devices can join and sync. Only the hosting device has to be one device at a time.

Does a Persistent Room work in the apps?

Yes. The Windows and Android apps use the same SharingCast page, so both My room and Join a room are available there too. For a host that should stay available all day, the apps are the better choice.

Can I still receive other files while a room is joined?

Yes. The Room tab and the Receive tab use separate connections, so a one-off transfer with a regular code works at the same time.

Is a Persistent Room less secure?

It is more predictable than a random code, which is why a password is essential. With a strong password, only people who know both can join and sync.

How do I stop using a Persistent Room?

On the host, open Room → My room and tap Stop room; use Remove all if you also want to clear its files. On a receiving device, tap Leave room under Join a room.

Can I send other files while my room is open?

Yes. The room runs on its own connection, so the Send tab works normally at the same time. Use it for one-off transfers to anyone, with a fresh random code.

Related guides

• Is peer-to-peer file sharing safe?
• Transfer files between two laptops
• Sync files between your PC and phone without the cloud
• Fix file transfer connection issues