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The best cloud backup services in 2021

Best Cloud Backup Services
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The best cloud backup services help you avoid data-loss disasters. That's because they automatically copy your most precious personal files to offsite cloud storage servers that you can reach from anywhere.

Cloud backup services exist because you can't always count on an external hard drive — one attached to your PC, or a drive on your local network — to provide the safest backups. 

A single theft, flood or fire could make you lose both your computer and its backup drive at the same time. Cloud backup services, also called online backup services, prevent total data loss in these situations. 

All the cloud backup services we've tested — Acronis True Image, Backblaze, Carbonite Safe, IDrive Personal, SpiderOak One and Zoolz Cloud Backup — protect your data on their servers with industry-standard encryption. They also let you encrypt your data again with your own private key if you choose. But if you lose that key, the service won't be able to help you recover the data.

Top 3 cloud backup solutions

1. IDrive is the best cloud backup solution right now
IDrive ranks highly on every review due to its great features and fair pricing. The software is available for Windows and  macOS computers as well as smartphones and tablets running Android or iOS, and there are command-line scripts for Linux machines.
View Deal

2. Backblaze is the easiest cloud backup solution
Backblaze is the easiest cloud storage solution to use  — just set it and forget it. It also has a useful restore-by-mail feature and rapid upload speeds. Backblaze is a great choice if you're looking for the best bang for your buck.View Deal

3. Acronis True Image is a powerful and versatile option
Acronis is a disk-imaging program with a cloud-storage component tacked on. It also happens to be (arguably) the most powerful online-backup solution available for consumers, and now includes antivirus software and ransomware protection.View Deal

News & Updates

— Acronis has added a vulnerability scanner to its Advanced and Premium packages to help detect software flaws.

— Carbonite has added Webroot SecureAnywhere antivirus software to its Plus and Prime packages.

— Backblaze has updated its Mac and Windows desktop software to version 7.0.2.

Cloud-backup services can vary greatly. A few let you back up operating-system files and applications. Some back up smartphones and tablets. 

Most of these services can back up files to a local drive as well as the cloud, and some let you share files with other people or provide file-syncing or dead-storage functions. And because backing up the entire computer for the first time can take days, a couple of these services even let you "seed" your cloud backups by mailing in a hard drive with your data on it.

But while some online-backup services let you back up an unlimited number of devices, and others give you unlimited online storage space, none of them gives you unlimited space for an unlimited number of devices for a flat price. That would just be too good to be true.

One last thing: Cloud backup services aren't always the same thing as cloud-based file-syncing services like Dropbox or Microsoft OneDrive. Nor are they exactly like file-archiving services such as Amazon Glacier. We explain the differences between these categories at the end of this buying guide.

What are the best cloud backup services?

Based on more than 40 hours of testing, our top pick among cloud-backup services is IDrive ($3.48 for the first year for Tom's Guide readers), which backs up an unlimited number of PCs, Macs, smartphones and tablets for a reasonable price. IDrive is the best choice if you have multiple computers and phones to back up, and it recently raised its already-generous storage caps.

Our value pick is Backblaze, which gives you unlimited storage for just $60 per year but backs up only one machine (and an external drive) per subscription. This is the best cloud backup service if you have a single Mac or PC and don't want to worry about the details.

Acronis True Image is the best choice for power users, offering a breathtaking assortment of useful features and a head-spinning number of pricing combinations. It's rather complicated and can be fairly expensive for the average home computer user.

SpiderOak is famed for its security and encrypts your data with a unique key that only you have. (Don't lose it.) However, subscriptions are quite pricey, so get SpiderOak only if protecting your data from prying eyes is your top priority.

Carbonite was once synonymous with cloud-backup software. Its consumer offerings seem affordable, but read the fine print: To get anything like iDrive or Backblaze's level of service, you'll have to pay a lot.

As for Zoolz Cloud Storage, we can't recommend it at the moment because the company no longer lists the service on its website. You can still buy a subscription, but it's not clear what you'll get. Until we hear further, hold off.

External hard drives stacked on top of laptop.

(Image credit: Boibin/Shutterstock)

The best cloud backup service you can get today

Best cloud storage service: IDrive Personal

(Image credit: iDrive)

1. IDrive Personal

The best cloud storage service overall

Number of devices: Unlimited | Storage limit: 10TB | External drive backups: Yes | Mobile device backups: Yes | System and application backups: Yes, but not by default | Two factor authentication: Yes | Drive shipping: Seed and restore

Free disk-shipping data-transfer option
Fast upload speeds
Backs up mobile devices
Generous syncing option
No unlimited storage option

IDrive offers the most bang for the buck, backing up an unlimited number of machines to either a 5TB ($3.48 for the first year for Tom's Guide readers) or a 10TB limit, which should be enough for most people. (These caps were recently raised from 2TB and 5TB, respectively.)

IDrive's upload speeds are fast, its mobile apps actually back up the devices they run on (and recognize faces in photos for easy tagging), it provides a generous file-syncing option and it even lets you mail in a full drive instead of spending days uploading data. 

IDrive also keeps old copies of each file forever, which is handy, but you'll have to mind those storage caps. It also has two-factor authentication, which is an essential feature every online service provider should offer.

Read our full IDrive Personal review.


(Image credit: Backblaze)

2. Backblaze

The best value in cloud storage services

Number of devices: 1 computer | Storage limit: Unlimited | External drive backups: Yes | Mobile device backups: No | System and application backups: No | Two factor authentication: Yes | Drive shipping: Restore only

Cheap, fast, easy and simple
Unlimited storage
Generous drive-shipping policy
No multiple-computer plans
Few extra features

Backblaze is still the cheapest online-storage solution, gigabyte for gigabyte, and it's the easiest to use. You literally can just set it and forget it. We also like the generous restore-my-mail feature and its rapid upload speeds. Backblaze even lets you locate a lost or stolen computer by geolocating the Wi-Fi network it connects to.

But Backblaze is not ideal for anyone who has multiple machines to back up, unless you have nearly unlimited storage needs. In that case, the reasonable yearly cost to back up each machine may be worth it.

Read our full Backblaze review.

Acronis True Image

(Image credit: Acronis)

3. Acronis True Image

The best cloud storage service for power users

Number of devices: Up to 5 computers | Storage limit: 5TB | External drive backups: Yes | Mobile device backups: Yes | System and application backups: Yes | Two factor authentication: No | Drive shipping: No

Full-disk-image online backups
Insane assortment of extra features
Backs up mobile devices
Expensive, with complicated pricing
Home users may not need all the features

Acronis True Image is a disk-imaging program with a cloud-storage component tacked on. 

But it's no kludge. Instead, it's perhaps the most powerful and versatile online-backup solution available. It offers mobile-device, external-drive and social-media backups, as well as syncing and sharing options. It even includes antivirus software, ransomware protection, a vulnerability scanner and a "survival kit" that quickly creates a bootable file-restoration tool. 

The downsides are that Acronis can get rather expensive and has a confusing pricing structure. But it's worth considering if you're a power user or someone who's shopping for antivirus software as well.

Read our full Acronis True Image review.

Carbonite Safe

(Image credit: Carbonite)

4. Carbonite Safe

Number of devices: Up to 5 computers, but no volume discount | Storage limit: Unlimited | External drive backups: Not with basic plan | Mobile device backups: No | System and application backups: No | Two factor authentication: Yes | Drive shipping: Restore only

Unlimited storage
Unique backup interface
Solid mobile experience
Slow download speeds

Carbonite offers unlimited storage. But you'd better read the fine print as it doesn't automatically back up large files, external drives, or any kind of video file on its Basic pricing tier. To get those functions, you'll have to trade up to the Plus or Premium plans, which have features similar to IDrive or Backblaze but cost much more. 

Multiple machines are supported on a single account, but there's no volume discount — each additional machine costs as much as the first. On the plus side, the software is attractive and easy to use.

Read our full Carbonite Safe review.

SpiderOak One

(Image credit: SpiderOak)

5. SpiderOak One

Number of devices: Unlimited | Storage limit: 5TB | External drive backups: Yes | Mobile device backups: No | System and application backups: Yes, but not by default | Two factor authentication: Only for legacy users | Drive shipping: No

Backs up unlimited devices
Strong sharing and syncing features
Focus on security
Steep learning curve
Cramped, confusing user interface

SpiderOak was the first online storage (or online-syncing) service to make sure the customer held a private, exclusive encryption key. 

Most other cloud storage services now offer the same thing, but SpiderOak also has strong file-sharing and -syncing features, as well as support for unlimited machines and, if you insist, backups of system files and applications. 

Yet SpiderOak's storage-space pricing is so high that it's more competitive with Dropbox than it is with IDrive. While its file-restoration speed was amazingly fast, its initial upload speed was glacial.

Read our full SpiderOak One review.

Zoolz Cloud Backup

(Image credit: Zoolz)

6. Zoolz Cloud Storage

Number of devices: Up to 5 computers, but only 1 per user | Storage limit: 4TB | External drive backups: Yes | Mobile device backups: No | System and application backups: Yes, but not by default | Two factor authentication: No | Drive shipping: No

Multiuser support
Intuitive, attractive user interface
Very slow file recovery
Useless mobile apps
Limited to single machine per user

Editor's note: Zoolz no longer seems to offer a cloud backup service for consumers. We're trying to get an answer from Zoolz about exactly what kind of cloud backup solutions it has for home users. Until then, we can't recommend this service.

Zoolz has a lot of features and an attractive, easy-to-use interface. The service permits multi-user accounts, lets you back up applications and system files and, at least at the time of this writing, is appealingly priced. 

But its Achilles' heel is that the Zoolz servers are just rented space on Amazon's Glacier dead-storage service, which is agonizingly slow to access. It doesn't help that the Zoolz mobile apps are next to useless.

Read our full Zoolz Cloud Backup review.

How we test the best cloud backup services

We took into consideration several factors: storage costs, ease of file restoration, computer-resource usage, unique features and ease of use and of installation. Upload speed also matters, because while your initial backup happens only once, the backup can take days or even weeks if it's several hundred gigabytes. 

We give bonus points to those online backup services that let you mail in a hard drive full of data to start the process or send you one to restore your data.

Our testing and evaluating was done on a 2017 15-inch Apple MacBook Pro booting into Windows 10. Mobile apps were run on a Google Pixel XL 2 running Android 8.1 Oreo. We monitored data-transfer rates on the MacBook with GlassWire, and CPU usage using Windows' built-in Resource Monitor.

Each cloud backup service was tested individually, then uninstalled from both devices before the next test. The test set of files to back up consisted of 16.8GB of documents, photos, videos and music. We uploaded this data to each service's cloud servers, then restored a 1.12GB subset of these files to the laptop.

The testing environment was a home in Middleton, Wisconsin, provisioned by TDS Telecom Extreme 300 Fiber internet service. Internet speeds during testing were typically 280 megabits per second (Mbps) down and 120 Mbps up, according to

Online backup vs. online syncing vs. online archiving

Cloud-backup services aren't the same as online-syncing services like Dropbox, Google Drive, iCloud or OneDrive

An online-syncing service's software creates a cloud-based mirror of a specific set of files or folders on your device, and pushes out identical copies of those files to all of your linked devices so that you can have immediate access to them. Think of the syncing service as the hub on a spoked wheel, with all your linked devices at the ends of the spokes.

Network cables plugged into servers.

(Image credit: asharkyu/Shutterstock)

Cloud-backup services are simpler. They continuously or periodically copy all or most of the files and folders on your computer to their own cloud servers. Instead of the spoked-wheel diagram of a file-syncing service, an online-backup service would look like a straight line between your machine(s) and the cloud server. 

Your data stays on those remote backup servers until you need it, and with luck, you never will. Most cloud-backup services offer generous amounts of storage for a subscription fee that is much cheaper, gigabyte for gigabyte, than an online-syncing service.

Cheapest of all are cloud-archiving services such as Box or Google Cloud. These let you offload files you don't immediately need to online servers, freeing up space on your hard drive. 

Cloud-archiving services can be dirt-cheap, sometimes as little as a few pennies per month per gigabyte, but there's often a fee to download files again. (The assumption is that you will never need to download all the archived files.) Backblaze has its own very affordable cloud-storage service called B2.

Combination lock resting on a circuit board.

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  • rocker60
    One needs a careful warning for iDrive. As a customer, I can say that their customer service will infuriate you. Here's the scenario:

    Had less than 5 TB to image for the iDrive Express service (i.e. included in pricing package). If you're a non-techie, you won't know that there is less than 5TB available on the 5TB Express Drive. Or... you just forget. Or you're "close", and figure you'll try it out. So you order the 5TB drive. Not big enough. Send it back.

    Upgrade to 10 TB because they won't send you a 10 TB Express Drive unless you sign up for the 10 TB service. Order 10 TB Express Drive. Won't send it to you free because you've already used your "one free per year". Send you a note to ask why you sent back an empty Express Drive and if you really meant to do that. Reference trouble ticket notes. No response.

    After one year. Request 10 TB drive to backup what is now 5.88 TB. Should be okay, right? Nope. Fails. 9.1 TB available isn't enough to do encrypted imaging on 5.88 TB because the encryption needs space to generate temporary files that are then deleted from your Express Drive. Total space needed? 11.3 TB. Told by support to send in 10 TB drive and order 20 TB Express Drive referencing technical support notes on ticket. Request for 20 TB drive denied. Why? "You have to upgrade to 20 TB storage to get a 20 TB drive."

    What...the...heck. So you want me to pay for 20 TB of storage to store 5.88 TB because y'all can't get your crap in a group and read trouble tickets and make a sane judgement? Company appears to be run out of a call center in India. No particular help from support or sales team. No one at iDrive who has a brain and the ability to actually just put a hard drive in a box to make a customer happy.

    BEWARE! iDrive support is horrible. Not sure what it would be like if I ever need to get a backup. At which point, I'm probably already going to be irritated, so probably not the best time to haver someone holding your data hostage. Caveat emptor, here, y'all. Each function is divided up into a "department" and "departments" don't/can't/won't talk to each other. Service promises much. Can't deliver on simplest functions of that.
  • ewolsh
    I agree about I-Drive.
    I also find BackBlaze problematic. I would say, it is not ready for prime time. The calling card seems to be the ease of use?, and lack of set-up required.? It's the little things, 1) The first time you want to recover a files your generated file list appears on a part of the screen that is not visible. You are looking at a black page- ESP helps to figure out what is going on. 2) no set up? that's great until they tell you - oh, they don't have any of your emails. .pst files aren't part of their saved files. They expect you to know this, because you are expected to have worked your way through their detailed set-up instructions, which are just as complicated as everyone elses. 3) Cuntomer service is only occationally available. And now it is email only. They used to have phone techs, some of whom were actually rude, With the nice ones, each one would tell you something different. Now with the e-mail, on a weekend, you have to monitor your email until they respond. That means you have found an alternative solution and the e-mail is irrelevant when it arrives. The answer chat bot is useless, it is easier to search the site yourself- you get the same or better answers... and then there was the time my hard drive blew up and I wanted to save it. I even payed extra to save it, but someone at BackBlaze just changed the name of the new computer, to the old computer name, and the additional saved hard drive disappeared. Luckily I was able to save oldhard drive- or I would have complained to who? Now I'm trying to get the account closed. Wish me luck.
    I miss Mozy!