Everything LinSync does

Which clouds

• Sign in with your browser: Google Drive, Dropbox, OneDrive, Box and pCloud. Your browser opens on the service's own page: sign in, press Allow, and that's it. You do it once.
• With an access key: Amazon S3, Backblaze B2, Wasabi, Cloudflare R2 and other S3 storage. Paste the key and the bucket.
• Not in the list: iCloud Drive and Proton Drive, which have no official way in. Choose them as a folder on this computer, and their own apps upload what LinSync puts there.
• Cloud services, in More, lists the clouds you've connected, says which backups use each, and has Check and Disconnect.

Google Drive, privately

LinSync signs in to Google as itself and asks only for the files it creates (Google's drive.file permission), so it can't see anything else in your Drive. The key Google gives it stays on your computer, readable only by you. Privacy.

The same safety as a drive

Copy, Mirror and Move work to a cloud (two-way Sync doesn't). Mirror keeps what it replaces or deletes in .linsync_archive in the cloud, the safety stop still applies, and a Trial run shows what would happen first.

Private if you want it

Sent as files, the cloud company can read what you store, as with any cloud. Choose a password zip and it's locked with AES-256 on your computer before it goes, so they can't. New backup's last page says which you've picked.

Worked out where each file is

The original's fingerprint is taken as it's read for copying, so it isn't read twice. On another computer, that computer works out the copy's fingerprint itself, many files at a time, so nothing comes back over the network to be checked. In testing, 50 files (60 MB) went to another computer in 2.4 seconds checked, against 1.8 unchecked.

Clouds and zips too

Cloud services keep a fingerprint of every file (Google Drive, Dropbox, Backblaze and the rest), and LinSync compares against it: only what that run copied, not the whole backup again. Zips are tested before they go, every file in them read back, a password zip with its password.

Never a bad copy in place

A copy only takes the real file's place once it has checked out. If it doesn't match twice, the file at the destination is left as it was, and the run tells you which one. That's usually a sign of a failing drive or a bad connection.

Seeing it, and switching it off

• New backup's last page says it: checked, every copy against its original by fingerprint.
• When a run finishes, the status says all checked, and how many were copied again, if any.
• For a backup where speed matters more, untick Check every copy against the original on New backup's last page, or Check every copy in Expert's middle. From the terminal: --no-check.
• Over SSH and to clouds, files are already protected while they travel. Checking also catches what can go wrong on either computer's disk.

One zip file

Everything you picked, packed into one zip with the date in its name, such as Holiday-2026-10-29.zip. Smaller to send, tidy to keep, and it opens on any computer with what's already built in.

A zip with a password

Locked with AES-256, the strong kind of zip encryption. You type the password twice. To open the zip you need that password, and 7-Zip on Windows, or Keka or The Unarchiver on a Mac: the unzip built into Windows and macOS can't open these.

A backup that runs by itself

In Simple, New backup now asks How should it arrive? A zip backup makes one new zip of the whole folder every time it runs, named with the date and time. Older zips stay until you delete them.

How it works

• Simple: step 4 of New backup, straight after where it goes. Pick a zip, and for a password zip type the password on the same page. A trial run shows the zip it would make. See the screen.
• Expert: the button under Copy selected says As files, As one zip or As password zip. Choose a zip, then drag or copy as usual, and LinSync asks for the zip's name (and the password) first. See the box.
• The zip is made in a temporary folder on your computer, copied across like any other file, then the temporary copy is deleted.
• Files on another computer or in a cloud can be zipped too: LinSync fetches them to this computer first, zips them, sends the zip on, then deletes its temporary copies.

Good to know

• 7-Zip does the locking. It comes inside the Mac and Windows downloads. The Fedora and Ubuntu packages bring in the system's own 7zip package.
• Tested every time. After making a zip, LinSync reads every file in it back against its checksum (a password zip with your password) and checks it's locked as it should be. If not, it throws the zip away and tells you. Then the zip itself is checked once it's arrived.
• Where the password goes. In Expert it's used for that one copy and never kept. A backup that runs by itself keeps it in your Mac's Keychain, or on Linux in the system's password store. Never in LinSync's own files, and never on a command line.
• Plain characters only. A zip password can use letters, numbers, spaces and keyboard symbols, but not accents or other alphabets: other unzip apps would read those differently and never open the zip.
• File names stay visible. A zip locks what's in each file, not its name, so someone without the password can still see what the files are called.

What they do

• Speed limit: No limit, 2, 5 or 10 MB/s for backups to your other computers and to clouds, so a big first upload doesn't slow down everyone else's internet. Copies on this computer, to a USB drive say, are never slowed down.
• Scheduled backups wait for the charger: on a laptop on battery, a scheduled backup waits up to three hours for mains power, then leaves it until its next time. A backup you start yourself always runs straight away.
• Tell me when a new release is out: on or off.

Safe by default

• Trial run lists every action before anything changes.
• Nothing is erased. Replaced and deleted files move to .linsync_archive/<date>/, kept for 30 days or as long as you choose.
• No half-written files. An interrupted run leaves nothing half-done.
• Missing folders stop the run, so an unplugged drive never looks like "everything was deleted".
• Safety stop: a run that would delete too large a share of the files halts on its own.
• Big files resume (4 MB and up) after a cancel or a dropped connection.
• Conflicts: newer wins, left wins, right wins, keep both, or skip.
• Every copy checked: its SHA-256 fingerprint against the original's, on by default. A copy that doesn't match is made again. More.
• Comparing: date and size (fast) or SHA-256 checksum, to decide what needs copying.
• Rules: exclude and include patterns, skip hidden files, minimum and maximum sizes.

Runs by itself

• Schedules: hourly, daily, weekly, at a set time, or every N minutes.
• Uses each system's own scheduler: systemd timers (or cron) on Linux, launchd on a Mac, Task Scheduler on Windows. LinSync doesn't need to be open.
• Watch mode: linsync watch re-syncs whenever something changes.
• Groups of tasks, plus your own commands to run before and after each one.
• Desktop notifications, and a log and run history for every task.

Type a password once

The first time you connect, you type the other computer's password. After that LinSync connects by itself, scheduled runs included.

Fast with small files

LinSync has its own SFTP client running over the system's ssh. Small files go in batches of up to 64, big ones stream at full speed: 600 small files took 1.7 seconds over a 30 ms link in testing.

Tailscale-aware

Find my computers lists your Tailscale devices. If Tailscale SSH asks you to confirm in a browser, LinSync opens the page and carries on once you approve.

Space

Inside LinSync (More…, then Space): click the folders and drives to look at, and see them as a ring chart. Zoom into folders, find the biggest items, drag a slice onto Delete (bin or permanent) or onto Copy / Move / Sync to turn it into a backup. System files and whole drives are protected.

System backup

Linux: a bootable copy of the whole computer on a USB drive that keeps itself up to date, encrypted with LUKS when your computer is. Start from it to test it, take single files back, or restore everything (UEFI with GRUB and dracut).

Mac and Windows: a home-folder backup (documents, photos, settings, mail) with older versions kept for 7 to 365 days and a Restore button.

Cloud-drive folders too

As well as going straight to the cloud: on a Mac, Proton Drive, Google Drive, OneDrive, Dropbox and iCloud Drive folders show up in Places and in the wizard. On Linux, folders such as ~/Dropbox and anything mounted with rclone mount. File dates are kept, so the next run copies only what's changed.

From the terminal

Everything the window does, you can script.

linsync new "Docs to USB" --left ~/Documents \
  --right /media/$USER/USB/Documents --mode backup_lr
linsync preview "Docs to USB"   # what would happen; changes nothing
linsync run "Docs to USB"
linsync schedule "Docs to USB" daily
linsync watch "Docs to USB"     # keep syncing as files change
linsync list                    # every task and when it last ran

Plain, open code

• Written in Python with Tkinter: no extra packages to install.
• The same code on Windows, Mac and Linux; the parts that differ live in one file.
• Over 200 automatic tests cover every mode, conflicts, the archive, the safety stop, SFTP, resuming, clouds and checking, including copies spoiled on purpose to make sure they're caught.
• Free software under the GNU GPL, version 3 or later.
• Prefer the original window? linsync classic is still there.