Back That Data Up
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Back That Data Up vs Arq
Arq has been a well-loved Mac backup app for years. Here is the honest picture of where BTDU adds features Arq does not, and where Arq is still the right pick.
| Back That Data Up | Arq | |
|---|---|---|
| Price | $29.99 one-time | $49.99 + $12/year storage |
| Local snapshots to any drive | ✓ | ~ |
| Cloud backup built in | ✓ | ✓ |
| Bring-your-own cloud (S3, Dropbox, etc.) | ✓ | ✓ |
| Post-quantum encryption on cloud uploads | ✓ | ✕ |
| Hardware key (FIDO2 / Yubikey) unlock | ✓ | ✕ |
| Ransomware anomaly detection | ✓ | ✕ |
| Verified restores every backup | ✓ | ~ |
| Self-healing cloud vault | ✓ | ✕ |
| One-time purchase | ✓ | ✕ |
✓ yes · ~ partial · ✕ no. Prices may change; verify before deciding.
About Arq
A well-designed cloud backup that has been around a long time
Arq has been a respected Mac backup app since 2009. Haystack Software (the company behind Arq) has been quietly serving Mac power users for the entire modern era of macOS backup. The Arq design is careful and considered: encrypted client-side, deduplicated on upload, backed up to whatever cloud storage you already use.
The bring-your-own-cloud model is where Arq shines. You point it at your Backblaze B2, Wasabi, S3, Google Drive, Dropbox, OneDrive, or SFTP account. Arq handles the encryption, chunking, and scheduling. Your data lives in your cloud provider, encrypted with keys only your machines hold. BTDU takes the same approach with Cloud Vault: your account, your storage, your keys.
Arq's cloud-first design is deliberate. If you already run Time Machine for local snapshots and just want a rigorous encrypted cloud backup on top, Arq has been the default recommendation for years and remains a solid pick.
Where BTDU adds features Arq does not is in the layers around the encryption itself: post-quantum crypto, physical-key unlock, ransomware anomaly detection, and self-healing when the cloud copy drifts from the local snapshot.
The honest gaps
Where Arq stops and BTDU keeps going
The Arq design was set before some of the threats and options that matter today existed. These are the gaps BTDU was built to cover.
No post-quantum encryption on cloud uploads. Arq encrypts your data with strong classical crypto. That is fine for today. But a backup lives for years or decades, and someone with access to your cloud storage can copy encrypted blobs today and sit on them until quantum hardware can crack them. BTDU 1.1 layers ML-KEM-768 (the NIST post-quantum standard) on top of X25519 via CryptoKit, so blobs harvested today stay opaque even after quantum arrives.
No FIDO2 physical key unlock on the vault. Arq unlocks with your passphrase. Anyone with your passphrase and access to your encrypted archive can open it. BTDU supports optional FIDO2 unlock with any Yubikey / SoloKey / Feitian / Nitrokey, verified at the crypto envelope — an attacker with your drive still needs the physical key.
No ransomware anomaly detection. Arq will happily back up encrypted files if that is what your Mac says the files are. It has no view into whether those changes are intentional or the work of ransomware. BTDU watches for mass encryption and mass deletion patterns and pauses the backup before compromised files overwrite the clean snapshots you would restore from.
No self-healing on cloud-side drift. If files in your Arq cloud archive get deleted (accidental delete, a sync client mishap, a family member "cleaning up"), Arq alerts you but does not automatically re-encrypt and re-upload from your local snapshots. BTDU 1.1 notices within the hour and heals the cloud vault from local, without you doing anything.
Recurring pricing. Arq's current pricing is $49.99 for the app plus $12 per year for cloud storage on their own service, or bring your own cloud storage that you pay for separately. BTDU is $29.99 one time, and Cloud Vault targets your existing cloud account with no BTDU-hosted backend.
Back That Data Up
Built for the gaps Arq's design predates
BTDU is not trying to be a better Arq. It is trying to be an app that ships features the modern threat landscape asks for and that Arq's older architecture does not include.
Post-quantum on cloud uploads
BTDU 1.1 encrypts Cloud Vault uploads with X-Wing, which combines X25519 (the classical curve you know) with ML-KEM-768 (the NIST post-quantum standard from FIPS 203) via Apple CryptoKit. This defends against store-now-decrypt-later: someone with cloud access copying your encrypted blobs today and cracking them when quantum hardware exists. Arq is strong on classical encryption; it does not yet ship a post-quantum layer.
FIDO2 key at the vault layer
BTDU supports unlocking your backup vault with any FIDO2 security key: Yubikey, SoloKey, Feitian, Nitrokey. Multiple keys per vault, so losing one does not lock you out. The key is verified at the crypto envelope, not just an app-launch UI gate, so a stolen drive still needs the physical key to open. Arq authenticates you with a passphrase. If your passphrase leaks, whoever has your backup blobs can open them.
Ransomware anomaly detector
BTDU watches every backup for mass encryption or mass deletion patterns and pauses before your clean snapshots can be overwritten. It works by monitoring the file change patterns ransomware produces. Arq faithfully backs up whatever you tell it to back up, including files a ransomware payload just encrypted. Anomaly detection is not part of the Arq design.
Self-healing cloud vault
If your Cloud Vault detects a missing or corrupted block, BTDU 1.1 re-encrypts and re-uploads from the local snapshot on the next backup. You do nothing. The cloud stays whole. Arq will notice a missing archive during a check operation and let you know, but does not automatically heal from local.
BTDU also ships local snapshots to any drive macOS mounts, which Arq does partially through its "Back up to local disks" mode but treats as a secondary use case. Local + cloud in a single app is a first-class BTDU design choice, not a bolt-on.
One more thing that does not fit neatly in a feature card: BTDU is sold as old-school software. You pay $29.99 once. Bug fixes and minor updates ship free for the life of the major version. There is no subscription, no renewal that doubles when you are not watching, and no account required to back up your own files.
The honest answer
Who should pick which
Stick with Arq if...
- → You already run Arq, it works, and adding post-quantum or FIDO to your threat model is not urgent.
- → You have a strong preference for a longer-tenured product with a large existing user base.
- → Ransomware is not a realistic threat in your workflow and you do not need anomaly detection.
Arq is a good app. If your threat model is passphrase-plus-encryption and you are on it, staying on it is a fine choice.
Consider BTDU if...
- → You care about the store-now-decrypt-later scenario and want post-quantum encryption from day one.
- → You want to lock the vault so only a physical FIDO2 key in your hand can open it.
- → You work with files ransomware would be catastrophic for (client work, source code, years of photos) and want anomaly detection on the backup side.
- → You want local snapshots and encrypted cloud vault as first-class equals in a single app.
- → You want to pay $29.99 once and be done with it.
A number of BTDU users came from Arq and kept Arq installed alongside during the transition. The two do not conflict. Point Arq at a different cloud target and BTDU at another, and you have two independent offsite copies until you decide which one you want to keep long term.
If BTDU sounds like a fit for what you need, here is where to start. $29.99, one time. No subscription, ever.
Already running Arq? Good. BTDU installs alongside it without conflicts. Run both for a while, then decide.