Corsair EX400

Introduction

If you've been stuck in the 1000 MB/s speed trap of traditional USB 3.2 external drives, the Corsair EX400U represents a genuine leap forward rather than an incremental upgrade. This USB4 external SSD targets mobile professionals, content creators, and anyone with a USB4 or Thunderbolt 4-equipped system who needs serious portable storage performance without sacrificing convenience. Available in 1TB, 2TB, and 4TB capacities, the EX400U delivers speeds that were previously exclusive to expensive Thunderbolt drives, but with a unique MagSafe-compatible magnetic ring that makes it particularly appealing for smartphone video recording and quick attachment to metal surfaces.

Product Overview

The Corsair EX400U measures 2.5 inches square and just under half an inch thick, weighing approximately 3 ounces in a compact aluminum and plastic construction. The aluminum top serves double duty as both a premium aesthetic touch and a passive heatsink, while the plastic sides and back keep weight down. The standout feature is the white magnetic ring on the underside that's compatible with MagSafe and Qi2 devices, allowing the drive to snap securely onto the back of compatible smartphones or any magnetic metal surface.

Under the hood, the EX400U employs the Phison PS2251-21 controller, a purpose-built 40 Gbps USB4 controller that's designed specifically for high-performance portable storage. The drive uses Kioxia 3D TLC NAND flash, which offers a solid balance between performance, endurance, and cost. Corsair includes a 40 Gbps USB Type-C to Type-C cable in the box, which is essential for achieving maximum performance since the drive is entirely bus-powered with no external power adapter required.

The drive supports USB4 at 40 Gbps, USB 3.2 Gen 2x2 at 20 Gbps, USB 3.2 Gen 2 at 10 Gbps, and maintains backward compatibility all the way down to USB 3.0 and 2.0. Corsair backs the EX400U with a three-year warranty and rates the drive at 1,400,000 hours mean time between failures. The 4TB model carries a 1,000 TBW endurance rating.

Performance & Real World Speed

Corsair rates the EX400U at up to 4,000 MB/s sequential read and up to 3,600 MB/s sequential write for the 2TB and 4TB models, while the 1TB version drops slightly to 3,500 MB/s reads with similar write performance. These are manufacturer-stated maximums that require a USB4 or Thunderbolt 4 connection to achieve. When connected to older USB 3.2 Gen 2 ports at 10 Gbps, you'll see speeds capped around 1,000 MB/s, while USB 3.2 Gen 2x2 at 20 Gbps will limit you to roughly 2,000 MB/s.

In real-world testing by multiple reviewers, the EX400U consistently exceeded its rated specifications, with some tests recording sequential reads above 4,000 MB/s when connected to proper USB4 ports. Write speeds typically landed between 3,550 and 3,700 MB/s in sustained transfers. For practical scenarios, this means transferring a 50GB 4K video project takes roughly 15 seconds instead of the minute-plus you'd experience with traditional 10 Gbps USB drives. Direct-to-drive ProRes video recording from an iPhone 16 Pro works seamlessly thanks to the magnetic attachment and sufficient sustained write performance.

The drive's sustained write performance after the SLC cache is depleted maintains speeds between 1,600 and 1,700 MB/s according to torture testing, which is substantially better than many competitors that drop below 1,000 MB/s when pushed hard. This makes the EX400U particularly well-suited for large file operations like backing up video footage or transferring entire game libraries, where sustained performance matters more than peak burst speeds.

Build Quality & Durability

The EX400U's construction balances portability with thermal management rather than rugged protection. The aluminum top panel provides a premium feel and serves as the primary heat dissipation surface, though it means the drive gets quite warm during sustained use. Testing shows surface temperatures can reach 69°C (156°F) under heavy continuous workloads, which is hot enough to be uncomfortable to touch but within normal operating ranges for high-performance SSDs. At idle, the case still reaches 41°C (106°F) on top and 35°C (95°F) on the underside with 23°C ambient temperature.

The plastic sides and back keep overall weight minimal, but this isn't designed to be a ruggedized, drop-proof solution like the Samsung T7 Shield or SanDisk Extreme Pro. There's no IP rating for water or dust resistance, and the compact size means it's easy to misplace. The included USB-C cable feels high-quality with solid connectors, which is important since you need a proper 40 Gbps cable to achieve rated performance. Aftermarket cables work fine, but make sure they're rated for USB4 or Thunderbolt speeds.

The magnetic ring is genuinely strong, providing secure attachment to iPhones, metal laptop cases, or even desktop PC chassis. This feature transitions from novelty to genuinely useful when you're recording video directly to the drive or need to temporarily park the drive somewhere accessible while working. Corsair's three-year warranty provides reasonable coverage, though it's shorter than the five-year warranties offered by some premium competitors.

Compatibility

The EX400U works with Windows 10 and later, macOS 13 and later, and maintains broad compatibility across ChromeOS, iPadOS, and iOS devices that support external storage. The drive ships formatted in exFAT for cross-platform compatibility out of the box, though you can reformat to NTFS for Windows or APFS for macOS if you're staying within a single ecosystem. Linux users will find standard plug-and-play functionality as well.

For console compatibility, the EX400U functions as external storage for PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X/S. On PS4 and PS5, you can store and play PS4 games directly from the drive, while PS5 games can be stored but must be transferred back to internal storage to play. On Xbox One and Xbox Series X/S, you can store and play Xbox One games from the external drive, but Series X/S optimized games can only be stored, not played, from external storage. The drive cannot be used for internal storage expansion on Xbox Series consoles, which require proprietary Seagate Storage Expansion Cards for that purpose.

The MagSafe ring works with iPhone 12 and newer models that support MagSafe, as well as other Qi2-compatible devices. This allows direct video recording to the external drive from supported devices, which is particularly useful for ProRes video on iPhone 16 Pro models. The magnetic connection is strong enough to hold the drive securely during normal handling but will release if the phone is dropped or roughly handled.

Critical compatibility note: you absolutely need a USB4, Thunderbolt 4, or Thunderbolt 5 port to achieve the advertised performance. Most current motherboards with AMD X870/X870E or recent Intel chipsets include USB4 ports, and many higher-end laptops now offer Thunderbolt 4. If your system only has USB 3.2 Gen 2 (10 Gbps) ports, you'll be limited to roughly 1,000 MB/s speeds, which means you're paying a premium for performance you can't utilize.

Strengths & Weaknesses

The Corsair EX400U delivers exceptional sequential performance that genuinely transforms external storage from a bottleneck into a viable working drive for professional applications. The ability to edit 4K video directly from the drive or transfer hundreds of gigabytes in minutes represents a substantial workflow improvement over traditional USB 3.2 drives. Real-world testing shows the drive meets or exceeds its rated specifications when properly connected, with sustained write performance that holds up well even during extended transfers. The compact form factor makes it genuinely portable, and the inclusion of a proper 40 Gbps cable in the box eliminates the need to hunt down compatible accessories.

The MagSafe magnetic ring moves beyond gimmick territory when you're actually using it to attach the drive to your phone for video recording or to temporarily mount it on a metal surface. The bus-powered design means no external power adapter to carry, and compatibility across Windows, macOS, Linux, and mobile platforms is seamless. Pricing at $199.99 for 2TB positions the drive competitively against Thunderbolt alternatives while offering broader compatibility through USB4 support. The drive supports modern features including TRIM, SMART monitoring, and garbage collection, with management available through Corsair's SSD Toolbox software.

However, the drive's thermal characteristics present legitimate concerns during sustained workloads. Surface temperatures exceeding 65°C (149°F) mean the drive becomes uncomfortably hot to touch during extended file transfers, and while this doesn't appear to cause performance throttling, it raises questions about long-term reliability and comfort during portable use. The lack of any rugged protection, water resistance, or shock absorption means this isn't a drive for field work in challenging environments. The three-year warranty is adequate but shorter than the five-year coverage offered by premium competitors like Samsung's T-series drives.

The value proposition depends heavily on your system's connectivity. If you lack USB4 or Thunderbolt 4 ports, you're paying for performance you cannot access, making cheaper USB 3.2 Gen 2 drives a more sensible choice. The drive also lacks hardware encryption features found on some security-focused portable drives, relying instead on software encryption if needed. Compared to building your own solution with a USB4 enclosure and internal NVMe drive, the EX400U offers convenience at the cost of some flexibility and potentially higher expense, though the integrated magnetic ring isn't easily replicated in DIY builds.

Against direct competitors, the EX400U stands out for USB4 performance at a lower price point than Thunderbolt 5 drives like the LaCie Rugged Thunderbolt 5, while offering substantially higher performance than USB 3.2 Gen 2x2 alternatives. The magnetic attachment feature is unique in this performance class, though thermal management lags behind some rivals.

Verdict: Should You Buy It?

Buy this if:

• You have a USB4 or Thunderbolt 4-equipped laptop or desktop and want to leverage that bandwidth for external storage

• You regularly work with large video files and need fast transfer speeds for 4K or higher resolution projects

• You own a MagSafe-compatible iPhone and want to record ProRes video directly to external storage

• You need portable storage that can genuinely function as a working drive rather than just backup storage

• You value the convenience of bus-powered operation without carrying an external power adapter

• You want substantially better performance than USB 3.2 drives without paying Thunderbolt 5 premium pricing

Skip this if:

• Your system lacks USB4 or Thunderbolt 4 ports and you'd be limited to USB 3.2 Gen 2 speeds (making cheaper alternatives more sensible)

• You need ruggedized storage with water resistance, shock protection, or military-grade durability for field work

• You're primarily using the drive for cold storage or backups where burst speed matters more than sustained performance

• You're uncomfortable with drives that run hot during extended use

• You prefer the flexibility and potential cost savings of building a DIY solution with a USB4 enclosure and internal NVMe drive

• You require hardware encryption for security compliance rather than software-based solutions