Part of the Cachet family
Cachet Drive keeps the folders you actually work in identical across your Macs, over your own network, and keeps an encrypted copy off-site. The folder stays a plain local folder, which is the whole reason your Mac stays fast.
Runs on macOS 15 and later. Signed and notarized. Your storage bucket, your keys.
A 5 MB file grows by one line. Only the block that changed crosses the network.
The problem
You keep a folder in a cloud drive because you want it on both machines. Then your Mac gets hot, the fan runs, everything feels sticky, and you cannot point at why.
It is rarely the uploading. A modern cloud drive installs a File Provider extension, which is a piece of system software that sits between every application on your Mac and the actual bytes on your disk. Every open, every directory listing, every check for whether a file exists, every append to a log has to go and ask it first.
For a folder of documents you touch a few times a day, you will never notice. For a source tree, a working set, or a folder that software writes to thousands of times a minute, that question gets asked so often that answering it becomes the workload. Your Mac is not busy copying your files. It is busy being asked about them.
Cachet Drive removes the thing in the middle. There is no File Provider domain and no kernel extension. The folder on your disk is a plain folder, indistinguishable from any other, and your applications talk straight to it at full speed. Synchronizing happens beside your work instead of in front of it.
Proof, with the conditions stated
Every figure here was measured on a real machine on a stated date. Where a number would move, we say what moves it. You can run the same measurement yourself.
Measured 2026-08-21 on a MacBook Air 15-inch (M5), running two cloud drive clients against 18,001 machine-written files totalling 30.2 GB, plus a 21,000-file configuration tree that is read on every process start.
| Measurement | With the cloud drive clients | With Cachet Drive |
|---|---|---|
| 1-minute load average | 87 | 11 |
fileproviderd processor time | 42% | 0.2% |
| A new file reaching the second Mac | queued behind the backlog | 18 seconds |
Conditions: both Macs on the same local network, no relay, block-level transfer
with local blocks reused. Your numbers will differ; the mechanism will not. Take the same
reading yourself with uptime and Activity Monitor before and after.
The off-site copy is measured separately, because a folder that changes constantly is the case where a backup either costs almost nothing or costs a fortune, and the difference is entirely in how it is sent.
Measured 2026-08-22 in a folder of large append-only records. In one ordinary day, 179 files changed, holding 662.5 MB between them, of which only a few megabytes were genuinely new content. The three rows below were measured on 59 of those files, holding 260.8 MB: the same bytes put through each method, so the comparison is like for like.
| How the copy is sent | Sent that night | Why |
|---|---|---|
| Whole files, the ordinary way | 260.8 MB | A file that changed at all is a file that gets sent again, all of it. |
| Changed parts only, standard blocks | 18.9 MB | Only blocks that moved are sent, but a big block carries a lot of unchanged bytes with it. |
| Changed parts only, high-churn blocks | 5.1 MB | Smaller blocks, so a one-line append drags almost nothing along behind it. |
One file, measured on its own so you can repeat it: a 3.01 MB record grew by one line, 76 bytes. Sending it whole costs 3,012,966 bytes. The high-churn engine sent 129,382. Both engines ship in the app and the choice is per folder, because the fast answer here is the wrong answer for most folders. See the off-site copy.
How it works
There is no drive to mount, no folder to move your work into, and no account to create. You point at a folder that already exists and it starts keeping up.
Any folder, anywhere on your disk. It stays exactly where it is and stays a plain folder. Nothing moves into a special location, so every path in every script you have keeps working.
A QR code appears on screen, or 56 characters you can paste. The other Mac reads it and the two introduce themselves directly. The code is checked and re-read at both full and small size before it is ever shown to you, so a code that would not scan never appears.
Changes cross your network as they happen, block by block, straight between your machines. Nothing routes through anyone's server. You never have to coordinate the two: work on either Mac whenever you like, and the moment both are awake on the same network they catch each other up from wherever they left off.
On a schedule you set, an encrypted copy lands in your own Cloudflare R2 or Amazon S3 bucket, with your keys. It only ever goes one way, so nothing in the bucket can come back and overwrite what is on your Mac.
What is in it
This list is the shipping build. Nothing here is a plan.
Five states: up to date, syncing, paused, needs you, engine down. It sits correctly in a light or a dark menu bar, and stays crisp on any display.
Icons in a synced folder carry their own state. Right-click gives you the actions where you already are: share this folder with a paired Mac, copy this Mac's code, pause, scan, or show earlier versions.
Build directories, dependency folders and caches are excluded by a preset rather than by you remembering. Presets are a plain file you can edit, not a list baked into the app.
One switch pauses the other sync clients on your Mac for a full-resource push, and names in plain words exactly what it paused so you are never guessing what changed.
High load on its own is usually just a queue, so it waits for high load and no idle processor time together, for five minutes, before it says anything at all.
Two Macs editing the same file leaves you both versions, labelled, and shows you where they are. Nothing is ever chosen for you and nothing is deleted.
The synchronizing engine ships inside the app, signed and notarized with everything else. Nothing to install first. If an engine is already running on your Mac it uses that one and starts nothing, because two engines fighting over one folder is how you get the conflicts this app exists to prevent.
--status prints the menu's own sentences, so a Mac with nobody sitting at
it can be checked from anywhere. Add --json and a script can read it.
--selftest checks the app's own logic against cases it must get wrong as
well as cases it must get right, so a pass means something. It exits nonzero on any
failure, which is what lets a script decide whether this Mac is healthy.
Where it earns its place
Thousands of small files, read constantly by tools that expect a local disk. This is the case where a mediation layer hurts most and where moving the folder off one buys back the most speed.
Logs, journals, transcripts, exports: files that grow by a little, constantly. They are cheap to keep in step and ruinous to copy whole, which is exactly what the high-churn engine is for.
A laptop and a desktop, or a machine at home and a machine that travels. Whichever one you open, the folder is the one you left.
Take the folders that change constantly off it and leave the documents where they are. The cloud drive gets quieter and faster too, because you have removed its hardest job.
When two Macs disagree
Editing the same file on two machines is not an error to be resolved automatically. It is two pieces of real work, and picking one for you throws the other away.
When it happens, both versions are kept and the second is named so you can tell them apart at a glance. The app finds them for you with a bounded scan: it stops at a file count and a deadline, and when it stops early it says so, so a short answer is never mistaken for a complete one.
From the right-click menu in the Finder you can keep the version in front of you, which moves the other aside with a timestamp, or show the two side by side first. Either way both files are still on disk when you are done.
The off-site copy
Synchronizing protects you from losing a Mac. It does not protect you from deleting something, because a deletion is a change and a change is what synchronizing faithfully copies. That is the job the off-site copy does.
Point it at Cloudflare R2 or Amazon S3 with credentials you created, scoped to that one bucket. The keys live in your Keychain and are handed to the engine in its environment at the moment it runs, so no configuration file on your disk ever holds a secret and no argument list ever carries one where another process could read it. We never see your data and we never hold your key, because there is no account here to hold it in.
Everything is encrypted on your Mac before it leaves. What lands in the bucket is ciphertext, including the file names.
Nothing in the bucket can come back and overwrite a local file. That means a mistake in the backup can never become a data loss event, which is the failure mode that makes people distrust backups in the first place. Anything replaced or deleted is kept, dated, so yesterday is still recoverable.
Most folders should be copied whole. It is simple, it keeps a full copy of anything it replaces, and for a folder that changes a little it costs nothing worth discussing.
A folder of large files that each grow every day is the opposite case. Copying whole files there sends hundreds of megabytes a night to move a few, and keeps a complete extra copy of every file it replaced, which is how a modest folder turns into tens of gigabytes a month of storage you are paying for.
So the high-churn engine sends only the parts of a file that actually changed, cut small enough that appending a line drags almost nothing along with it. On the folder measured above, that is 5.1 MB instead of 260.8 MB for the same day's changes. You choose per folder, in Settings, and the standard engine stays the default because for most folders it is the right answer.
A backup that has never been restored is a hypothesis. This one is checked by restoring real files and comparing them to the originals byte for byte, and the engine can be asked at any time whether a recent restore actually worked, in one word.
Next to the alternatives
Prices read from each company's own pricing page on 2026-08-22 and linked, so you can check them. Compared on the axes that decide this particular choice.
| Cachet Drive | Dropbox | iCloud Drive | Syncthing on its own | |
|---|---|---|---|---|
| Folder stays a plain local folder | Yes | No, a File Provider extension mediates it | No, a File Provider extension mediates it | Yes |
| Sync any folder where it already lives | Yes | Inside the Dropbox folder | Inside iCloud Drive | Yes |
| Files travel directly between your Macs | Yes, on your network | Via Dropbox servers | Via Apple servers | Yes, on your network |
| Encrypted off-site copy in a bucket you own | Yes, R2 or S3, your keys | Their storage | Their storage | Not included |
| Only the changed parts sent off-site | Yes, on folders you choose it for | Not applicable | Not applicable | Not included |
| Finder badges and right-click actions | Yes | Yes | Yes | No |
| Set up by a person in a few minutes | Yes, a QR code | Yes | Yes | Configuration in a browser |
| Price | $79 once unlimited Macs |
$9.99/mo dropbox.com/plans |
from $0.99/mo apple.com/icloud |
Free syncthing.net |
A cloud drive and this are not the same purchase, and we would rather say so than pretend. A cloud drive is built for documents a person edits and shares, with links, comments and a web view. Cachet Drive is built for folders that change constantly and are read by software. Take those off the cloud drive; leave the rest where it is.
Privacy
Most of this section is short because most of the usual answers do not apply here. We do not have your files, because they never come to us.
Directly, on your own network. Relays and global discovery are off unless you turn them on. There is no server of ours in the path and no account for one to belong to.
Into a bucket you own, with keys you made, scoped to that bucket. Contents and file names are both ciphertext. Your storage bill, not ours.
The app counts which features you use so it can show you your own usage in Settings. Those counts use a fixed vocabulary of feature names, which is what makes the file incapable of holding a file name, a path or a device name rather than merely unlikely to.
A diagnostic bundle is prepared when you ask for one, and you can read it before it goes anywhere. Nothing is uploaded on its own.
What is underneath
Syncthing does the synchronizing, under the Mozilla Public License 2.0, and its source is public. Its license travels inside the app bundle and the About window names the project and points at it. rclone moves the standard off-site copy, under the MIT license. The high-churn engine is ours, compiled into the app so it needs nothing installed on your Mac.
Naming these is deliberate. Every performance and privacy claim on this page can be checked against those projects rather than taken on our word, which is the point of saying it. Cachet Drive is the product around them: the setup, the presets, the pairing, the status, the conflict handling, the two off-site engines, and the watch that tells you when your Mac is genuinely struggling.
Questions
Three separate mechanisms answer this. Two edits to one file produce two files, both named, so a winner is never picked for you. The off-site copy runs one way, so a file in the bucket is never written back over a local one. And a file that copy replaces or removes is written into a dated folder first, which is what makes yesterday recoverable. Resolving a conflict from the Finder menu moves the other version aside with a timestamp, so the version you did not keep is still on disk afterwards.
Both versions are kept, the second is renamed so you can tell them apart, and the app shows you where they are. You resolve it from the right-click menu in the Finder when you are ready, and keeping one moves the other aside with a timestamp instead of deleting it.
No, and that is close to the whole idea. You point at a folder that already exists, wherever it is, and it stays there as an ordinary folder. Every path in every script you have keeps working.
You do not have to coordinate them. Work on either Mac whenever you like; the two catch each other up once both are awake on the same network, picking up from wherever they left off. On battery it can pause itself entirely and resume when you are back on mains, and it only resumes the folders it paused itself.
You. Everything is encrypted on your Mac before it is sent, file names included, so what the storage provider holds is ciphertext. The keys are yours, in your Keychain, and the credentials are scoped to that one bucket so they are refused anywhere else.
Because that extension is asked a question on every file operation your Mac performs in that folder, not only when something is uploaded. For a folder that software reads and writes thousands of times a minute, answering those questions becomes the work. Removing the layer removes the questions.
How much gets sent. The standard engine copies a changed file whole. The high-churn engine cuts files into small pieces by content and sends only the pieces that changed, so a one-line append to a large file sends a few hundred kilobytes rather than the whole file. Measured on 59 real transcript files holding 260.8 MB, one day's changes cost 5.1 MB instead of 260.8 MB. You pick it per folder, and it is fixed for that folder once chosen, because the pieces only match pieces cut the same way.
Yes. --status prints the same sentences the menu shows, and
--status --json gives a script the same information. That is how a machine
running with nobody at it gets verified.
No, and we would rather be direct about that. A cloud drive is for documents people edit and share, with links and comments and a web view. This is for folders that change constantly and are read by software. Moving those onto this makes both faster.
macOS 15 and later, on Apple silicon. It is signed with a Developer ID and notarized by Apple, and it updates itself from our own feed with every update checked against that same signature before it is installed.
Pricing
One purchase, not a subscription. We hold none of your files and run no servers for you, so there is nothing here to rent you.
$79 once
Every folder, every Mac you own, and the encrypted off-site copy into your own bucket. Priced per person rather than per machine, because the whole product is about the second machine and taxing that would be taxing the point of it.
$0.015 per GB per month
Paid to your storage provider, not to us, because the bucket is yours. That is Cloudflare R2's own rate, with no charge for getting your data back out. The folder measured on this page costs cents a month to keep off-site.
A subscription would mean charging you rent on software that only ever talks to your own machines, and there is no good answer to the question that invites. One price, one time, and the version you buy keeps working.
Get it
Install it, pick a folder, show the other Mac the code. Then take a load average reading before and after and see whether the number moved on your machine.
macOS 15 and later, Apple silicon. Signed with a Developer ID and notarized by Apple. Updates itself, and checks the signature of every update before installing it.
# see what it is doing, from anywhere, without a screen
"/Applications/Cachet Drive.app/Contents/MacOS/CachetDrive" --status
# make it prove its own logic against decoys it must fail
"/Applications/Cachet Drive.app/Contents/MacOS/CachetDrive" --selftest