What Kopia is
Kopia describes itself as a cross-platform backup tool for Windows, macOS and Linux. It offers fast incremental backups, client-side end-to-end encryption, compression and data deduplication, and it ships with both a CLI and a GUI. The project is licensed under Apache 2.0.
The Windows GUI is called KopiaUI. For command-line fans, a third-party winget catalog lists the package ID as Kopia.KopiaUI, installable with winget. That catalog says it works on Windows 10 builds that support winget (1809 or newer).
On version status: the GitHub releases page lists v0.23.1 as the latest release, a bugfix for a rare race condition that might lead to data loss. The project recommends upgrading. Its release timestamp is June 16, 2026. If you installed an earlier build, update before you rely on it.
Why snapshots beat copy-and-hope
Shah's main point is that classic backup tools make you copy folders over and over. Kopia works differently. In Kopia's terms:
- A snapshot is a point-in-time record of the files and folders you chose.
- A repository is the storage location where snapshots live. It is always encrypted with a password you set.
- A policy is the rule set for scheduling, retention, compression and exclusions.
According to Kopia's getting-started guide, after the first snapshot, Kopia rescans your files and uploads only content not already in the repository. That also covers files you moved or renamed. Kopia's feature documentation adds that it uses rolling-hash file splitting, so a modified large file uploads only its changed parts, not the whole file.
That is slightly more precise than the "only new or modified content" description in the XDA piece. Kopia stores content it hasn't seen before, so a small edit to a big file doesn't mean re-uploading every byte.
Deduplication is automatic. Kopia's FAQ says it is on for every repository whether you use the GUI or CLI, so you don't need to turn anything on.
Getting started in KopiaUI
Here is the basic flow, per Kopia's documentation:
- Install KopiaUI and launch it. On first run it asks you to create a repository.
- Pick a storage type. For an external drive or NAS, choose Local Directory or NAS and enter the directory path. Kopia says any readable attached directory works, including USB devices, SMB shares and SSHFS mounts.
- Set a repository password. Kopia encrypts all repositories by default, so there is no unencrypted option.
- Open the Policies tab, enter or browse to the folder you want to protect, and click Set Policy.
- Choose your policy settings and click Save Policy. Kopia then starts taking snapshots according to those settings.
- Set a Snapshot Frequency. Kopia's guide notes that without one, snapshots don't run automatically, and you must click Snapshot Now on the Snapshots tab each time.
That last point matters. The XDA piece describes "set it and forget it" automation, but that only holds if you actually configure a frequency.
Where your backups go, and who pays
This is where Kopia's flexibility shows. Its documentation lists these destinations:
- Amazon S3 and S3-compatible storage
- Azure Blob Storage
- Backblaze B2
- Google Cloud Storage
- WebDAV and SFTP servers
- Local and network-attached storage
- Your own Kopia Repository Server
- Selected Rclone-supported services. This path is experimental, and only Dropbox, OneDrive and Google Drive are documented as tested through Rclone.
Kopia's documentation says plainly that the software is free and the storage is not. You must provision and pay for whatever storage provider you use, then point Kopia at it. A free backup app is not a free off-site backup. For a cloud bucket, you create an account, create a bucket and obtain credentials before Kopia can use it.
Two copies, with a catch
XDA suggests keeping one repository on an external SSD and another in the cloud. That is sound advice, but Kopia's guide says it doesn't natively save one snapshot to multiple repositories. The workaround is to connect desktop KopiaUI to several repositories at once and create matching policies for each. The guide says that option, reached by right-clicking the app icon and choosing Connect To Another Repository..., is available only in the desktop app, not the web-based UI.
Kopia's FAQ also warns that KopiaUI tries to connect to every file ending in .config in its config folder, which is %APPDATA%\kopia on Windows. If you keep test configs there, rename them so they don't end in .config.
The password warning
If you remember one thing, make it this. Kopia's documentation says the repository password never leaves your machine. It is used locally to protect the repository's primary encryption key. There is no recovery path if you lose it, and that includes your file and folder names, not just the contents.
Practical details from the FAQ:
- The default cipher is AES256-GCM-HMAC-SHA256. CHACHA20-POLY1305-HMAC-SHA256 is available under Show Advanced Options when you create the repository.
- You can't change the encryption algorithm after the repository exists.
- KopiaUI can't change the password. You need the CLI command
kopia repository change-password, and you must still be connected to the repository. - Kopia recommends storing the password in a password manager.
One more caveat from the docs: Kopia allows one password per repository and has no access control. Sharing a repository with another person or machine means sharing the password, and with it access to everything in the repository.
Restoring and verifying
KopiaUI offers three restore methods from the Snapshots tab. You can mount a snapshot as a local drive and copy files out. You can restore a whole snapshot to a local or network location. Or you can download individual files by browsing the snapshot.
Kopia's feature page says it can often recover from partial repository loss because index data is stored redundantly. It also says it cannot recover data if the actual backup data file in the repository is corrupt, and it advises running repository consistency checks regularly. A backup you've never test-restored is only a hope.
Is it really replacing traditional backup?
Not entirely. Kopia's README is explicit that it does not image your whole machine. It backs up the files and directories you choose. That makes it a strong fit for documents, photos, project folders and work files. It does not replace a system image or recovery media if you want to rebuild Windows exactly as it was.
A separate Kopia library README, now archived, carries a blunt warning for cautious readers: don't trust all your data to one tool, and keep another backup. That README is old, so treat it as a general principle rather than a statement about today's release. Third-party reviews also describe the interface as functional but not especially polished. That is a minor point against a free tool.
Bottom line
Kopia is a capable file-and-folder backup option. It is encrypted and incremental, it deduplicates, and it keeps version history. It also gives you a real choice of destination without a subscription tied to the app. To use it well on Windows:
- Run v0.23.1 or newer.
- Store the repository password in a password manager before you make the first snapshot.
- Set a snapshot frequency and review your retention and exclusion rules.
- Budget for the storage you choose.
- Add a second destination if you want off-site protection.
- Test a restore, and run consistency checks on a schedule.
Whether that's enough to make your current backup routine feel outdated depends on how many of those boxes you already tick.