Solid-state drives (SSDs) have come a long way in recent years: a long way up in speed and capacity, and a long way down in price.
Technology that was previously reserved for enterprise customers and the PC performance elite has gained the common touch, with mainstream desktops and laptops now featuring SSDs rather than hard drives as primary storage choices.
And adding an internal SSD to an older PC as a new boot drive remains a great, cost-effective upgrade.
If you're still relying on spinning metal, you'll find it one of the easiest ways to an instant, undeniable speed boost.
That said, while almost any SSD is much faster than any hard drive, not all SSDs are created equal—not by a long shot.
SSD interfaces have evolved greatly of late, and SSDs themselves are taking on different shapes and core technologies.
This guide will help you sort through the different confusing terminologies associated with SSDs, as well as learn what you need to know when it comes to pricing, speeds, durability, warranty durations, and more.
Are You Upgrading a Laptop or a Desktop?
First, some context on the difference between internal and external SSDs.
Most of what you need to know is obvious from the name.
"Internal" means the drive goes inside a desktop PC or laptop, while "external" means it connects to a computer via a cable.
But it's good to know some nuances regarding how fast each kind can be.
External SSDs are drives with their own standalone enclosures, which plug into your laptop or desktop via a USB cable or (less commonly) a Thunderbolt 3 cable.
Most are built for portability, with some small enough to fit on a keychain.
On average (because of the limitations of current bus technology), the higher end of the sequential speed spectrum you should expect to see over Thunderbolt 3 or USB 3.2 Gen 2x2 is in the range of 2,500 megabytes per second (MBps) for reads and 2,000MBps for writes.
Internal SSDs are more complicated.
You'll see them in three main physical forms: (1) 2.5-inch drives, (2) M.2 drives, and (3) add-in-board (AIB) SSDs.
Within those three physical forms are some crucial variations, though.
M.2 drives and AIB SSDs transfer data between the drive and computer via one of two bus types: the same Serial ATA bus used by 2.5-inch drives, or the PCI Express bus, the lanes and pathways of which can also be used by other hardware, such as graphics cards.
(If you'd like a deep overview of all the SSD terms shoppers should know, check out our SSD dejargonizer for a full breakdown.)
When buying an internal SSD to upgrade or augment a system you own, start by figuring out what your system can actually accept: a 2.5-inch SATA drive only? Does it have an M.2 slot? What length of M.2 drive can it take, and using which bus type? If you're upgrading a laptop, in most cases you'll have the option only to swap out the internal drive, not to add another.
If you can't get the info off the web beforehand, or from the manufacturer, you'll need (in most cases) to open up your laptop to see whether you have upgradable storage in the first place.
(That is, if you can open it at all.) With laptop upgrades, you typically have much less flexibility than upgrading a desktop; your only option might be buying a drive in a higher capacity than the existing one, since you'll likely have only one M.2 slot or 2.5-inch bay to work with.
(See our favorite SSDs for laptop upgrades.)
For a desktop, the right SSD to buy depends much more on what you are doing and what your aim is.
If you're building a new PC from scratch, you definitely want an internal M.2 or 2.5-inch SATA SSD as your boot drive nowadays.
A 2.5-inch SATA drive might only make sense if you're upgrading or building from older hardware; almost all new motherboards now have at least one M.2 slot of some kind, and these drives save lots of space in compact PC builds.
If you're installing an SSD as a secondary drive, you can probably choose between 2.5-inch or M.2, especially if it's a game or backup drive.
At capacities of 4TB or above, 2.5-inch SATA drives are often much cheaper than their M.2 counterparts.
Take the new SATA-based Samsung SSD 870 EVO, for example, which retails for $479 for the 4TB version, while the M.2 Sabrent Rocket Q 4TB goes for a whopping $829.99.
In these scenarios, choosing a SATA-based option that still keeps up in 4K random read and writes is the value move, and will give you more budget to play with when upgrading the rest of your system.
And if you're simply replacing a hard drive as your boot drive, you'll love the speed boost.
We guarantee it.
What Form Factor of SSD Do You Need?
We've introduced you to M.2 drives and 2.5-inch drives above, but let's get into them in a bit more detail.
2.5-Inch SSDs: The Basic Drive
The 2.5-inch Serial ATA SSD is the most common type of internal solid-state drive you'll encounter.
It was one of the earliest consumer-facing implementations of SSD technology and remains wildly popular, especially for upgrading older PCs.
While the drive electronics are much smaller than 2.5 inches, its enclosure will measure a bit wider (actually 2.75 inches wide, despite the name), so it will fit into the same mounting brackets in your desktop or laptop used by 2.5-inch hard drives.
That makes them your most likely choice for upgrading a platter-based boot drive in an older laptop.
And almost any desktop PC nowadays will have 2.5-inch bays, or let you boot a 2.5-inch drive in a 3.5-inch hard drive bay.
If you're upgrading an older laptop, you'll also want to account for the thickness of a 2.5-inch SSD.
Almost all SSDs nowadays conform to a 7mm thickness, but older laptops with SATA hard drives may have drive bays with as much as 9.5mm clearance.
Some SSD makers bundle a space-filling frame with their drives to keep a thinner 7mm drive from rattling around in a roomier bay.
That's less common today than in years past, though.
M.2 Drives: Stick-of-Gum Speedsters
M.2 slots are increasingly common in new desktop motherboards and practically universal in late-model laptops. M.2 solid-state drives are the 2.5-inch drive distilled to its essence, extremely minimal in their design and implementation.
They're also the most complicated to understand before you buy.
First, consider the bus type.
M.2 drives come in SATA bus and PCI Express bus flavors, and the drive requires a compatible slot to work.
Some M.2 slots support both buses on a single slot, but no drives can support more than one, so make sure the SSD you buy matches the bus type available on the slot in question.
M.2 drives also come in different lengths.
Physically, the most common of five M.2 SSD sizes is what's known as Type-2280, shorthand for 22 millimeters wide and 80mm long.
(All SSDs you'll see for consumer PC upgrades are 22mm wide; lengths range from 30mm to 110mm.) Most are merely circuit boards with flash memory and controller chips on them, but some M.2 drives (especially those of the PCI Express 4.0 variety) now ship with relatively large heatsinks mounted on top to keep them cool.
If an M.2 drive you're looking at has one of these special, big heatsinks on it, make sure your desktop's motherboard has the clearance above and around it to accommodate its bulk.
Some desktop motherboards situate an M.2 slot right alongside the ideal expansion slot you'd use for your graphics card, for example, and the hardware can collide.
Laptop designs typically can't stomach a special, tall heat sink at all.
What Bus Type of SSD Should You Buy?
Let's get into the issue of bus type in a little more depth.
Oftentimes, you won't have a choice of what bus variety you need.
But you need to know some background to figure out what you have and what you should buy.
SATA: The Old Standard
Serial ATA is both a bus type and a physical interface.
SATA was the first interface that consumer SSDs used to connect to motherboards, like the hard drives that preceded them.
It's still the primary cable-based interface you'll see for 2.5-inch solid-state drives.
The SATA interface is capable of sequentially reading and writing a theoretical maximum of 600MBps in an ideal scenario, minus a bit for overhead processes.
Most of our testing has shown that the average drive tops out at roughly 500MBps to 550MBps; in sequential tasks, the real-world difference between the best SATA drive and a merely average one is pretty small.
However, there's also the matter of 4K random read and write performance to consider.
4K random read and write speeds reflect how quickly the drive performs in day-to-day tasks; think booting Windows 10, launching games, loading levels in those games, or working in applications like Adobe Photoshop.
For most gamers and general users, 4K random read/write speeds are going to determine how much you actually feel the "speed" of a drive, and should be the most important spec to keep in mind if you plan on turning your next SATA-based SSD into a boot drive or backup storage for your trove of games or creative projects.
SATA-based SSDs like the Samsung SSD 870 EVO have shown that in 4K random read and write, specifically, SATA isn't quite out of the game yet, offering performance in loading games or applications that's on par with...
PCI Express: Where Speed Is Going
The original implementation of the PCI Express interface for SSDs took the form of cards that occupied one of the PCIe slots on a desktop motherboard, and you can still find carrier cards that let you plug M.2 drives into a standard PCIe slot.
Nowadays, though, the most popular PCI Express SSDs mount into an M.2 slot, though as we said above, you should make sure that your M.2 slot (assuming you have one in the first place) supports PCIe drives before you make your purchase.
Some support only the SATA bus; some support PCIe only; and some support both.
A further wrinkle around the PCIe bus: Some drives and some slots support a newer transfer protocol known as NVMe (for Non-Volatile Memory Express).
NVMe is a standard designed with flash storage in mind (opposed to the older AHCI, which was created for platter-based hard drives).
In short, if you want the fastest consumer-ready SSD, get one with NVMe in the name.
You'll also want to be sure both drive and slot support NVMe.
Some early M.2 PCIe implementations supported PCIe but not NVMe.
PCIe 3.0 NVMe SSDs have been the standard for a number of years, but now with the launch of the third- and fourth-generation Ryzen processors from AMD (and PCIe 4.0 support for Intel rumored to be on the way), PCIe 4.0 is setting new peak-speed records for consumer storage.
On the market, you will find three iterations of PCI Express drives in production right now: PCIe 3.0 x2, PCIe 3.0 x4, and PCIe 4.0 x16 (the "x" in each of these naming schemes refers to how many lanes the drive has available to transfer data).
A mainstream choice is a PCIe 3.0 x4 drive; you'll only want to consider a 4.0 model if you have a very new AMD Ryzen-based desktop based on the X570, B550, or TRX40 chipsets.
(Check the specs for PCI Express 4.0 support, and on which slots, before you dive in.)
Even PCIe 3.0 is significantly faster than SATA in straight-up sequential runs, though, and the interface is set to get even faster over the coming years as PCIe 4.0 makes its way into the mainstream.
What Capacity Do You Need, and What's the Cost per Gigabyte?
Okay, you've figured out the bus type, interface, and form factor of the drive you need.
The next factor to look at in determining your next SSD purchase is the capacity of the drive.
A lightly used Windows or macOS machine shouldn't need a drive larger than 250GB or 500GB as the main boot drive, but gamers and content creators will need to get at least 1TB in order to store sufficient games and 4K video comfortably on their drives.
On a desktop, they may also want to consider offloading their game library or video scratch disks onto cheaper, roomier hard drives.
That said, with games like Call of Duty: Modern Warfare requiring over 100GB of space just for one title, the drive could end up full again faster than you can line up a sniper shot.
These days, if you're looking to get just one drive (or maybe you have to, such as in a laptop), 2TB is the recommended size for gamers, while hardcore content creators who are dealing with 8K RAW footage will need far, far more.
(A one-hour 8K RAW file will occupy 7.92 terabytes of space.)
But big drives don't come cheap (especially when you're talking about SSDs rather than hard drives), so knowing the value of an SSD and how much it costs per gigabyte is another important factor to weigh in your next upgrade.
Whether it's 128GB or 4TB (or any capacity, really), the cost per gigabyte will give you a baseline to compare one drive against another and whether or not it looks like a good value based on its features and durability rating.
On average, an internal SSD can cost anything from 9 or 10 cents per gigabyte (example: the 2.5-inch SATA-based Mushkin Source, with 1TB for just a bit more than $90) to...
