ArcCaster Help

ArcCaster links the computers you already own so they behave like one machine: drag a file from one to another, watch a screen live and take over its keyboard and mouse, or open a terminal on any of them. Everything here is written for the version you have in front of you.

What ArcCaster is

ArcCaster is a desktop app you run on each computer you want to link. The computers talk to each other directly — peer to peer, over your own network or a cable between them. There is no account to create, no cloud service in the middle, and your files and screens do not travel through anyone else's servers.

Because it connects computers to each other, it has to be running on both ends. A machine with ArcCaster closed is invisible to the others.

It runs on Windows, macOS, Linux, and Android, and machines running different operating systems link to each other normally — a Mac can watch a Windows screen, a Linux box can pull files from a Mac.

Install it everywhere

Install ArcCaster on every device you want to link, then open it on each one. That is the whole setup. There is nothing to configure before two machines can find each other, as long as they are on the same network.

Leaving it running in the background is the normal way to use it: a machine that is open and idle costs almost nothing, and it means the others can reach it whenever you need them to.

The permission prompts

The first launch asks your operating system for a few permissions. Each one unlocks a specific feature, and declining one only switches that feature off — the rest of the app keeps working.

Permission	What it is for	If you decline
Firewall / network access	Letting other machines start a connection to this one	You can still connect outward, but nobody can reach you
Screen recording / screen sharing	Sharing this screen so others can watch it	Your screen appears black or blank to everyone else
Accessibility / input monitoring	Letting a remote user's keyboard and mouse control this machine	They can watch, but clicks and keys do nothing
Files and folders	Reading and writing the folders you browse	Some folders show as empty or refuse writes
Microphone	Adding your voice to a recording	Recordings capture system sound only

On macOS, screen recording and accessibility permissions often do not take effect until you quit and reopen ArcCaster. If you granted a permission and the feature still does not work, restart the app before assuming it failed.

You can grant any of these later from your system settings — you are not stuck with a decision made on the first run.

Finding your other computers

ArcCaster looks for other copies of itself on your local network automatically. Open it on two machines on the same Wi-Fi or the same switch, wait a few seconds, and each appears in the other's Connections strip.

If discovery doesn't find it

Automatic discovery relies on a type of network message that some networks block — guest Wi-Fi, corporate networks with client isolation, and some VPNs all commonly do. When that happens you can add the other machine by hand, which always works as long as the two can reach each other at all.

On the machine you want to reach, find its address under This computer's addresses.
On this machine, type that address into Add a peer manually and confirm.

A manually added peer is remembered, so you only do this once per machine.

A VPN on either computer is the single most common reason two machines on the same Wi-Fi cannot see each other. Most VPN apps route all traffic through the tunnel, including traffic meant for the machine sitting next to you. Look for a "local network" or "split tunnelling" option and allow local addresses.

The fleet password

A fleet password is a shared secret that all your machines know. Set the same one on each machine and they will accept each other and refuse everything else — useful on a network you share with people you do not fully control, like an office or a flat share.

Set it from Connections → Fleet Password. Every machine needs the same value; a machine with the wrong password is simply not admitted.

A tour of the window

The header

The top of the window carries the ArcCaster name, the licence button, and — at the right — the language dropdown and the light/dark toggle. Change either at any time; the app switches immediately and remembers your choice.

Connections

Every machine ArcCaster can see appears as a tile. A tile shows the machine's name, how it is connected, and — if that machine is sharing its screen — a live thumbnail of it. Click a tile to work with that machine.

Tiles can also show CPU and memory load, so you can spot a machine that is struggling without opening anything. Turn that on under Connections → Show CPU/RAM on tiles.

Files

The file panes are how you move things around: your own folders on one side, a connected machine's folders on the other. You can open more than one pane at a time from Files → View → Multiple File Panes when you are moving things between several machines at once.

Transfer queue and log

Everything ArcCaster is doing or has done shows up here — transfers in progress, transfers that failed, connections coming and going. When something does not behave, this is the first place to look, and the messages are written to be read rather than decoded.

If you would rather see more of your machines and less of your files, Files → View → Fleet View hides the file panes entirely.

Transferring files

Drag a file from one pane to another and it copies. That is the short version, and for most people it is the whole story.

You can also use Copy, Cut, and Paste between panes, rename, delete, move to trash, and open a file's properties, all from the right-click menu — the same actions you would expect from your normal file manager.

The transfer queue

Transfers queue up and run in order, so you can drop a large batch and walk away. Each one shows its progress, and anything that fails stays visible with the reason it failed rather than disappearing silently.

If a transfer failed because the connection dropped, reconnect and press Retry failed — you do not need to hunt down which files did not make it.

Big files and full disks

ArcCaster checks the destination before it starts, so you find out about a problem up front instead of at 90%:

Not enough space — you are told how much the transfer needs and how much is free, so you can pick another drive.
Read-only destination — the folder or drive will not accept writes.
Over 4 GB — the destination drive is formatted FAT32, which cannot hold a single file larger than 4 GB no matter how much space is free. Use a drive formatted exFAT, NTFS, APFS, or ext4 instead.

Watching a screen

Open a connected machine's screen and you see it live. This is a real video stream, not a series of snapshots — you can watch someone work, follow a video, or keep an eye on a long build.

The stream adapts to the connection you have. On a fast link you get a smooth, sharp picture; on a slow or busy one, ArcCaster reduces quality rather than falling behind, so what you are looking at stays current.

To see how the stream is actually performing — frames per second, decode time, network round trip, packet loss — turn on the overlay under Connections → Show FPS/GPU overlay on screens.

Taking control

While watching a screen, choose Take control and your keyboard and mouse go to that machine instead of this one. Your clipboard goes with you, so you can copy text here and paste it there.

Press Ctrl + Esc to release control and get your own machine back. This works even if the remote machine has stopped responding, so you can never get stuck.

While you are in control, the title makes it obvious — the window says which machine you are driving and reminds you how to let go.

Control needs the remote machine to have granted its accessibility or input permission. If you can see the screen but nothing you type or click has any effect, that permission is the reason — see Control isn't working.

Multiple monitors

When the machine you are watching has more than one monitor, ArcCaster shows you all of them and lets you decide how they are laid out on your screen. You can drag each monitor into position, and they snap to each other's edges so the arrangement lines up cleanly.

You can lay them out by pixel size, or by physical size — a 27-inch monitor next to a 15-inch laptop looks like what it actually is, which makes it much easier to tell which screen you are looking at.

Your arrangement is saved per machine, so a setup you fix once stays fixed. Plug in a different set of monitors and ArcCaster treats that as a new arrangement rather than forcing your old one onto it.

Recording, with sound

You can record a screen you are watching, with its audio, to a video file. Choose the folder recordings go to, the audio format and bitrate, and whether to include your own microphone alongside the machine's sound — useful for narrating what you are doing.

Audio buffering is adjustable. A smaller buffer means less delay between what happens and what you hear; a larger one is more forgiving of a busy network. If sound breaks up, raise it.

If the recorder hits a problem mid-way it starts a new file and carries on rather than losing the recording. You will see a note in the log when this happens, and you will have more than one file at the end.

Remote terminals

Open a command line on any connected machine, from this one. It behaves like a terminal sitting in front of that computer: run commands, watch output scroll, work normally.

Open one from the Terminal menu or by clicking a headless machine's tile. On machines with no screen of their own, the tile shows the open terminal instead of a thumbnail.

If you want to see at a glance what is happening on each machine, Mirror terminals on tiles puts each machine's terminal output onto its tile.

Admin tools

The Admin menu holds the things you would otherwise open several windows to do:

Run command on all — send one command to every machine at once, and see each machine's answer.
System info — hardware, operating system, and load for a machine.
Processes — what is running, with the ability to kill a process or copy its PID.
Services — start, stop, restart, and inspect background services.
Reboot, Shut down, Lock screen — power control, with a confirmation before anything drastic.
Switch User — change which account a machine is logged in as.
Fleet event log — connections, disconnections, and errors across every machine in one list.

Some of these need administrator rights on the target machine. If a command comes back refused rather than failed, that is usually what happened — check Admin Terminal Settings for how that machine runs elevated commands.

Cable, Wi-Fi, or LAN

ArcCaster uses whatever link the two machines have, and tells you which one it picked. The differences are large:

Link	Roughly	Good for
Thunderbolt or USB4 cable	Hundreds of megabytes per second	Everything — large transfers, high frame rate screens
Wired Ethernet	Tens of megabytes per second	Comfortable for anything most people do
Wi-Fi	Varies enormously	Fine day to day; the first thing to blame when it isn't

A direct cable between two computers is dramatically faster than Wi-Fi and completely private, since the traffic never touches your network at all. If the two machines sit near each other and you move large amounts of data, one cable is the single biggest improvement available to you.

You do not have to choose. Plug a cable in and ArcCaster starts using it; unplug it and it falls back to the network on its own.

Quality and frame rate

Each screen you watch has its own quality and frame rate setting, and there are defaults for new screens under Connections → Default Quality and Default FPS.

Match window (sharpest) streams at exactly the size you are viewing at, so nothing is scaled twice and text stays crisp. It is the best choice when you are reading or working rather than just watching.

Lower quality or a lower frame rate is the right answer on a slow link. Rather than freezing and catching up in bursts, ArcCaster stays live at a quality your connection can actually sustain.

What actually limits speed

When a screen is slower than you expect, the network is usually not the culprit — people assume it is, and it usually isn't. In rough order of how often they matter:

The link type. Wi-Fi with a weak signal, or a power-saving Wi-Fi adapter, beats every other cause combined.
Capture cost on the sending machine. Grabbing a very large or very high-refresh screen takes real work.
Whether hardware video encoding is available. A machine with a working GPU encoder does this almost for free; one without spends CPU on it.
What the sending machine is otherwise doing. A machine pinned at 100% CPU has nothing left for streaming.

The overlay under Show FPS/GPU overlay on screens tells you which of these is biting, instead of leaving you to guess.

Headless servers

A machine with no monitor — a server in a cupboard, a spare box under a desk — can join your fleet and be managed entirely through its terminal. Connections → Admin → Set up a headless server gives you the exact command to run on it.

Once set up, it joins automatically and rejoins every time it boots, so you can reboot it remotely without losing it. Its tile shows its terminal rather than a screen thumbnail.

AI agents

ArcCaster can let an AI agent running on your own computer use your fleet the same way you do — run commands, move files, look at screens.

It is off until you turn it on, under Connections → Allow AI Agents on This Computer, and the app explains exactly what you are granting before you agree.

Only agents running as you, on that computer, can connect — nothing is opened to the network. You can switch it back off from the same menu at any time.

Turning it on for one machine gives an agent on that machine access to the whole fleet, because that is what your own account can already reach. Turn it on where you are working, not everywhere.

Settings and preferences

Language — 41 languages, switchable at any time from the header or More → Language.
Light and dark — follows your operating system on first run, and remembers any change you make.
Show intro at startup — the welcome screen; switch it off once you know your way around, or replay it from More → View intro.
Suppress warnings — quietens confirmations you have decided you do not need.
Show Advanced — reveals the deeper tuning options for people who want them.
Auto-connect — links up with a discovered machine on its own, and reconnects when a cable is replugged.

ArcCaster also keeps a machine awake while it is being watched or is transferring, so a screen you are working on does not go to sleep under you.

Licence and trial

ArcCaster starts with a free trial so you can use the real thing before deciding. The header shows how many days remain.

When you are ready, Get License opens the licensing window inside the app, where you can compare plans, buy, or enter a key you already have. The green globe button beside it takes you straight to the web purchase page instead, which is where payment methods the app cannot host live — Apple Pay among them on the Mac page.

A licence covers a number of machines. Your plan and seat count are shown in the licensing window, and Add Devices is where you extend it.

Nothing can connect to me

What you see

You can see other machines and connect out to them, but nobody can start a connection to you. ArcCaster may tell you this directly — it notices when it can see other machines but nothing has ever reached it.

Why

A firewall is blocking incoming connections on this machine. This is the most common single problem people hit, and it is easy to miss because half of everything still works.

Fix

Allow ArcCaster through your firewall for incoming connections. On Windows this is the prompt that appeared on first run — if you clicked Cancel, the rule was never created.
Check both the operating system firewall and any security suite you have installed; they are separate, and either can block it.
A blocked connection times out rather than being refused, so slow failure is the symptom to expect.

I can't see the other computer

Check in this order

Is ArcCaster actually open on it? It has to be running on both ends.
Are they on the same network? Two Wi-Fi networks with similar names, or one machine on a guest network, is a common trap.
Is a VPN running on either machine? This is the most likely answer if everything else looks right. Allow local network traffic, or disconnect the VPN to test.
Does the network block discovery? Guest and corporate Wi-Fi often isolate clients from each other. Add the machine manually by address — if that works, discovery was being blocked.

The connection dropped

What happens

ArcCaster reconnects on its own when the other machine comes back, and tells you it is waiting rather than failing silently. Transfers that were interrupted stay in the queue.

What to do

Once it reconnects, press Retry failed to resume anything that was interrupted.
If it does not come back, check the other machine is powered on, awake, and still has ArcCaster running.
Repeated drops on Wi-Fi usually mean signal or power saving rather than a fault — see The screen is slow or stuttery.

Thunderbolt stopped working

What you see

A cable link that was working stops and does not come back on its own, often right after a sleep, a power change, or plugging something else into the same cable.

Why

The link itself has wedged at the hardware level. ArcCaster cannot revive it from software, which is why it tells you plainly rather than retrying forever.

Fix

Unplug the cable and plug it back in, the way it was when it worked.
Make sure the other machine is powered and running ArcCaster.
It reconnects automatically once the link is healthy — you do not need to restart anything.

A transfer failed

Read the message first

ArcCaster says which of these it is, so you do not have to guess:

Won't fit — not enough free space. The message tells you how much is needed and how much is free.
Read-only — the destination will not accept writes. Pick another folder, or fix the permissions there.
Over 4 GB — the destination drive is FAT32, which cannot store a file that size at all. Use an exFAT, NTFS, APFS, or ext4 drive.
Connection lost — reconnect, then Retry failed.

The screen is slow or stuttery

Try in this order

Turn on the FPS overlay. It shows frame rate, decode time, round-trip and loss, which tells you where the problem is instead of leaving you guessing.
Suspect Wi-Fi power saving. Bursty response times and occasional loss on an otherwise fine network is the classic signature. Setting the adapter to maximum performance fixes it outright.
Lower the frame rate before the quality. Fewer, better frames usually feels better than more, worse ones.
Use Match window. Streaming at the size you are actually viewing avoids scaling the picture twice.
Check the sending machine's load. A machine at 100% CPU has nothing left to encode video with.
Try a cable. If the two machines are near each other, this ends the conversation.

The screen is frozen

Frozen picture, healthy numbers

If the image is stuck but the overlay still reports a healthy frame rate, frames are arriving — the sending machine is repeating the same one. Closing the screen and reopening it restarts capture and clears this.

Black or blank instead of frozen

A black screen almost always means the screen recording permission was never granted on the sending machine, not that the stream failed. On macOS, grant it and then reopen ArcCaster.

Control isn't working

You can see the screen, but nothing responds

The remote machine has not granted the permission that lets a program send it keyboard and mouse input — accessibility on macOS, input monitoring or an equivalent elsewhere. Watching needs one permission; controlling needs another, which is why one works without the other.

Fix

Grant accessibility or input permission to ArcCaster on the machine being controlled.
On macOS, quit and reopen ArcCaster afterwards.
Make sure you actually took control — watching alone does not send input.
If you cannot get your own mouse and keyboard back, press Ctrl + Esc.

No sound

Check the sending machine is actually playing something, and is not muted at the system level.
If sound breaks up rather than being absent, raise the audio buffer — that trades a little delay for stability.
For microphone audio in a recording, confirm the microphone permission was granted and the right input device is selected.

A permission was denied

Nothing is permanent. Grant the permission in your system settings, then reopen ArcCaster — on macOS especially, a permission granted while the app is running often does not take effect until it restarts.

If a feature is disabled because a tool is missing rather than a permission being denied, ArcCaster names the missing tool in the log. Install it and the feature comes back.

Text is clipped or wrong

If a translation is cut off or overflows its space, that is a bug in the layout rather than anything you did — please report it with your language and a screenshot and it will be fixed.

If the app is in a language you did not choose, it followed your system language on first run. Set the one you want from the header dropdown; your choice is remembered from then on.

Keyboard shortcuts

Shortcut	Does
`Ctrl` + `Esc`	Release control of a remote machine and return to your own
`Ctrl` + `Alt` + `T`	Open a terminal
`Ctrl` + `Shift` + `Esc`	Task Manager on a controlled Windows machine
`Ctrl` + `Up`	Mission Control on a controlled Mac

While you are in control, shortcuts go to the machine you are controlling — that is the point. Ctrl + Esc is the exception, and always brings you home.

Privacy and security

Peer to peer. Machines talk directly to each other. Your files and screens do not pass through our servers, because there are no servers in the path.
No account. There is nothing to sign up for and no identity to link your machines to.
Your network only. ArcCaster connects over your own network or a cable between two machines.
A shared secret if you want one. A fleet password means only machines that know it are admitted.
Permission by permission. Screen sharing, control, files, and microphone are separate grants, and you can decline any of them and keep the rest.
AI agent access is off by default and limited to agents running as you, on that computer.

Glossary

Term	Means
Fleet	All the machines running ArcCaster that can see each other
Peer	Another machine running ArcCaster
Tile	The card in Connections representing one machine
Seat	One machine covered by your licence
Headless	A machine with no monitor, used through its terminal
Discovery	Machines finding each other on the network automatically
FPS	Frames per second — how often the screen you are watching updates
Round trip	How long a message takes to reach the other machine and come back

Still stuck?

If this page did not answer it, the frequently asked questions cover what ArcCaster can and cannot do. For anything else, get in touch and a human will read it.

When reporting a problem, the transfer log is the useful part — it records what ArcCaster was doing and what went wrong, and it saves a great deal of guessing.