CFexpress
CFexpress is a high-performance standard for removable flash memory cards developed by the CompactFlash Association (CFA), designed to meet the demands of professional imaging, videography, and industrial applications through the use of the PCI Express (PCIe) interface and NVMe storage protocol.[1] Introduced as a unified successor to earlier formats like XQD and CFast, it supports three form factors—Type A (compact for smaller devices), Type B (matching XQD dimensions for broad compatibility), and Type C (larger for higher capacities)—with theoretical maximum transfer rates reaching up to 4 GB/s in its current implementations (Type B with CFexpress 4.0). While Type B is widely used, Type A sees limited adoption in select devices, and Type C has no commercial products as of 2025.[1] The standard incorporates the Video Performance Guarantee (VPG) certification to ensure reliable sustained write speeds for high-frame-rate and high-resolution video recording, such as 8K RAW footage.[2] The development of CFexpress began with the CFA's announcement of the family on September 6, 2016, aiming to provide scalable, low-latency storage with up to 8 lanes of PCIe Gen3 for theoretical speeds of 8 GB/s.[3] The first specification, version 1.0, was released in 2017, focusing on PCIe Gen3 x2 lanes for maximum rates of 2 GB/s and initially emphasizing the Type B form factor for compatibility with existing XQD-enabled cameras.[1] Version 2.0, released in 2019, introduced Type A (PCIe Gen3 x1, up to 1 GB/s) and Type C (x4, up to 4 GB/s) form factors alongside Type B (x2, up to 2 GB/s), and enhanced power efficiency for battery-powered devices like mirrorless cameras.[1][4] In August 2023, the CFA unveiled CFexpress 4.0, which adopts PCIe Gen4 and NVMe 1.4c to double throughput potential over version 2.0 while ensuring full backward compatibility to protect existing investments in cards and hosts.[5] CFexpress cards are widely adopted in professional digital single-lens reflex (DSLR), mirrorless, and cinema cameras from manufacturers such as Nikon, Canon, and Sony, enabling burst shooting rates exceeding 100 frames per second and uncompressed video workflows.[1] Their robust metal enclosures provide thermal management and durability for demanding field conditions, with capacities ranging from 80 GB to 2 TB or more depending on the form factor and version.[1] The standard's emphasis on interoperability and future-proofing positions it as a key technology for evolving media requirements in 4K, 6K, and 8K production environments.[3]Overview
Definition and Standards Body
CFexpress is a high-speed removable flash memory card standard designed for professional applications, including 8K video recording and high-resolution burst photography.[6][7] It enables reliable handling of large data volumes in demanding workflows, such as continuous raw image sequences and uncompressed video streams.[8] The CompactFlash Association (CFA), a non-profit industry organization, serves as the standards body responsible for defining and maintaining the CFexpress specification.[9] Established to promote interoperable removable media solutions, the CFA oversees the development of protocols and physical interfaces to ensure compatibility across devices.[1] In 2016, the CFA chartered the creation of CFexpress as a unified removable media standard intended to span diverse market segments, from photography and videography to industrial and broadcast applications.[5] This initiative aimed to consolidate fragmented formats into a single, scalable architecture supporting evolving storage needs.[9] The core objective of CFexpress is to provide sustained high-throughput data transfer for resource-intensive tasks, utilizing a PCIe-based interface with the NVMe protocol to achieve efficient, low-latency performance.[9]Core Technology and Purpose
CFexpress leverages the NVM Express (NVMe) protocol over a Peripheral Component Interconnect Express (PCIe) physical interface to deliver low-latency, high-bandwidth storage solutions for demanding data transfer needs.[10][11] NVMe optimizes command queuing and parallel processing for non-volatile memory, while PCIe provides a scalable, high-speed serial bus that supports simultaneous bidirectional data flow, enabling transfer rates significantly exceeding traditional interfaces like SATA.[11] This combination ensures efficient handling of large volumes of data with minimal overhead, making it suitable for environments requiring rapid read and write operations.[10] At its core, CFexpress relies on NAND flash memory, a non-volatile storage technology that retains data without power, enhanced by built-in mechanisms for reliability and longevity. Error correction codes (ECC) detect and repair data errors, maintaining integrity during high-speed operations, while wear leveling algorithms distribute write cycles evenly across memory cells to prevent premature degradation.[12][13] Additionally, power-efficient designs minimize energy consumption, which is critical for battery-powered portable devices, allowing sustained performance without excessive drain.[13][11] These features collectively provide robust, dependable storage that supports professional workflows where data loss or downtime is unacceptable.[10] The primary purpose of CFexpress is to serve as a high-performance removable media standard for professional and prosumer applications in digital imaging and media production. It targets scenarios such as professional photography and videography, where continuous high-bitrate recording—such as RAW 8K video at 60 frames per second—demands exceptional sustained write speeds and reliability.[10][11] In broadcast environments, it facilitates seamless capture of uncompressed or lightly compressed footage, enabling creators to handle complex shoots without storage bottlenecks.[10] This focus on speed and durability positions CFexpress as an essential tool for industries evolving toward higher resolutions and frame rates.[11]History and Development
Origins from Predecessor Formats
The CFexpress standard emerged as a response to the fragmentation in high-performance memory card formats within the professional imaging industry. The CompactFlash Association (CFA) had previously developed CFast in 2009, a SATA-based successor to the original CompactFlash cards that offered improved speeds but retained a larger form factor similar to traditional CF Type I and II cards, limiting its adoption in more compact devices.[14] In parallel, the CFA introduced the XQD format in late 2011, with its first commercial implementation in Nikon's D4 camera in 2012; early XQD utilized a PCIe interface constrained to a single lane of PCIe 2.0, capping theoretical transfer speeds at around 500 MB/s, while later versions supported up to two lanes for approximately 1 GB/s, still restricting scalability for emerging high-bandwidth applications like 4K and 8K video.[15][16] By 2016, the CFA recognized the need to consolidate these divergent paths—CFast's SATA limitations and XQD's lane restrictions—into a unified standard to streamline development for manufacturers and reduce market confusion. In September of that year, the CFA announced CFexpress as this unifying format, leveraging the more scalable PCIe interface with NVMe protocol support to enable multi-lane configurations for higher throughput while aiming for backward compatibility with existing XQD slots through adapter mechanisms.[17][9] The initiative addressed key shortcomings, such as CFast's bulkier design that hindered integration into slimmer camera bodies and XQD's inability to fully exploit PCIe potential beyond two-lane operation, positioning CFexpress as a future-proof solution for professional photography and videography.[18] Early development efforts focused on prototypes that bridged these predecessors, with the CFA finalizing the CFexpress 1.0 specification in April 2017 to support initial PCIe Gen 3 implementations. Delkin Devices played a pivotal role in these integration trials, releasing the first commercially available CFexpress 1.0 cards in June 2017, which demonstrated practical viability by achieving sustained speeds exceeding those of XQD and CFast in compatible test environments.[19] These prototypes underscored the CFA's commitment to unification, paving the way for broader industry adoption by resolving compatibility issues and enhancing performance scalability without requiring entirely new hardware ecosystems.[9]Version Releases and Milestones
The CFexpress 1.0 specification was released by the CompactFlash Association in the second quarter of 2017, marking the initial standard for the format with support for PCIe Gen3 interface and restriction to the Type B form factor.[1] This version laid the groundwork for high-performance storage in professional imaging devices, achieving theoretical maximum throughputs of up to 2 GB/s through two lanes of PCIe 3.0.[20] In the first quarter of 2019, the CompactFlash Association announced CFexpress 2.0, which expanded the ecosystem by introducing three form factors—Types A, B, and C—while maintaining backward compatibility with 1.0 devices.[1] This update doubled the theoretical throughput potential for certain configurations by leveraging additional lanes, with Type B cards supporting up to 2 GB/s and Type C enabling up to 4 GB/s via four PCIe 3.0 lanes.[4] The specification facilitated the first widespread integration into consumer cameras, notably the Canon EOS R5 released in 2020, which utilized Type B cards for 8K video recording. The CompactFlash Association unveiled CFexpress 4.0 in the third quarter of 2023, upgrading to PCIe Gen4 for enhanced performance while ensuring full backward compatibility with prior versions across all three form factors.[5] Type B cards under this standard achieve theoretical throughputs of up to 4 GB/s, supporting demanding applications like high-frame-rate 8K workflows. By early 2025, commercial cards adhering to the 4.0 specification became available from manufacturers including ProGrade Digital and Angelbird, with models offering capacities up to 2 TB and sustained write speeds exceeding 2 GB/s.[21][22] As of late 2025, manufacturers like Sony and Lexar released CFexpress 4.0 Type A cards with capacities up to 2 TB, further expanding options for high-resolution workflows.[23] Key milestones in CFexpress development include the CompactFlash Association's 2023 announcement of version 4.0, which emphasized support for 8K RAW video and high-resolution imaging to meet evolving professional needs.[24] Notably, the association skipped a 3.0 iteration, jumping directly to 4.0 to align with PCIe Gen4 advancements and streamline efficiency in the specification roadmap.[1]Technical Specifications
Interface Protocol and PCIe Implementation
CFexpress employs the NVM Express (NVMe) protocol as its command set, enabling efficient queue-based operations that support up to 65,535 queues with 65,536 commands per queue, significantly reducing protocol overhead compared to the Advanced Host Controller Interface (AHCI) used in predecessor formats like CFast. This NVMe implementation over PCIe allows for parallel command processing and low-latency data transfers, optimized for non-volatile memory subsystems in high-performance storage applications. At the physical layer, CFexpress utilizes the PCI Express (PCIe) serial interface with differential signaling for reliable high-speed communication, where data is transmitted over pairs of wires to minimize noise and electromagnetic interference. The CFexpress 2.0 specification incorporates PCIe Gen3, operating at 8 GT/s per lane, while the CFexpress 4.0 upgrade adopts PCIe Gen4 at 16 GT/s per lane to enhance bandwidth without altering the core protocol structure.[5] Lane configurations vary by card type to balance performance and form factor: Type A uses a single PCIe lane (x1), Type B employs two lanes (x2), and Type C supports four lanes (x4), allowing scalability for different host requirements.[25][26] Electrically, CFexpress operates at a 3.3V power supply, compatible with standard host interfaces, and includes hot-plug support to enable safe insertion and removal without powering down the system, leveraging PCIe hot-plug capabilities for seamless connectivity in professional environments.[27] For data integrity during high-speed transfers, CFexpress incorporates PCIe link-layer error handling mechanisms, including cyclic redundancy check (CRC) for frame validation and automatic retry protocols to retransmit corrupted packets, ensuring robust transmission across the serial lanes.Performance Characteristics by Version
CFexpress memory cards have evolved across versions 1.0, 2.0, and 4.0, with performance improvements driven by advancements in PCIe generations and lane configurations. Version 1.0, released in 2017, primarily supported the Type B form factor using PCIe Gen3 x2, delivering a theoretical maximum throughput of 2 GB/s.[1] Version 2.0, introduced in 2019, expanded to include Type A (PCIe Gen3 x1, 1 GB/s), Type C (PCIe Gen3 x4, 4 GB/s) alongside Type B (PCIe Gen3 x2, 2 GB/s), while adding support for smaller capacities and enhanced compatibility.[1] Version 4.0, announced in 2023, leverages PCIe Gen4 to double these figures, achieving 2 GB/s theoretical for Type A (Gen4 x1), 4 GB/s for Type B (Gen4 x2), and 8 GB/s for Type C (Gen4 x4), with backward compatibility to earlier versions and hosts.[5] No commercial Type C cards are available as of November 2025. In practice, real-world speeds fall below theoretical maxima due to encoding overhead (approximately 985 MB/s per PCIe Gen3 lane after 128b/130b encoding) and host limitations, but they still enable high-performance workflows. CFexpress 2.0 Type B cards typically achieve sequential read speeds of 1400-1700 MB/s and write speeds of 1400-1500 MB/s in benchmarks, as seen in tests with cards like the Sony CEA-G series.[28] For CFexpress 4.0, 2025 tests show Type B cards reaching up to 3700 MB/s read and 3600 MB/s write, exemplified by the Nextorage B2 Pro and Angelbird AV Pro models, though sustained writes may drop to 3000-3500 MB/s under prolonged loads.[29][22] Type A cards in version 4.0, such as the Nextorage NX-A2PRO series, deliver practical reads up to 1950 MB/s and writes up to 1900 MB/s when paired with compatible readers.[30]| Version | Type A Theoretical Max | Type B Theoretical Max | Type C Theoretical Max | Example Practical Speeds (Read/Write, MB/s) |
|---|---|---|---|---|
| 1.0/2.0 | 1 GB/s (Gen3 x1) | 2 GB/s (Gen3 x2) | 4 GB/s (Gen3 x4) | Type B: 1700/1480[28] |
| 4.0 | 2 GB/s (Gen4 x1) | 4 GB/s (Gen4 x2) | 8 GB/s (Gen4 x4) | Type B: 3700/3600[29]; Type A: 1950/1900[30] |
Physical Design
Form Factor Types
CFexpress memory cards are available in three distinct physical form factors—Type A, Type B, and Type C—each designed to address specific requirements for size, compatibility, and application in photographic and video equipment. These variants allow manufacturers to integrate high-performance storage into devices ranging from compact mirrorless cameras to larger professional setups, while maintaining a common NVMe over PCIe interface.[1] Type A cards feature a compact design measuring 20 × 28 × 2.8 mm, introduced with the CFexpress 2.0 specification to suit space-constrained environments. This form factor supports single-slot implementations in mirrorless cameras, such as those in the Sony Alpha series, prioritizing portability without sacrificing essential functionality.[36][4] Type B represents the standard form factor at 38.5 × 29.8 × 3.8 mm, making it the most widely adopted variant for digital single-lens reflex (DSLR) and mirrorless cameras, including models like the Nikon Z9. Its dimensions and connector match those of XQD cards, facilitating backward compatibility with existing XQD slots through firmware updates rather than requiring physical adapters.[1][37] Type C cards adopt a larger profile of 54 × 74 × 4.8 mm, targeted at high-end cinema and broadcast applications in rack-mounted or professional video equipment where greater physical robustness and capacity integration are beneficial. Despite its potential for demanding workflows, this form factor remains less adopted owing to its size, with no commercial cards or compatible cameras available as of November 2025.[4][1]Dimensions and Compatibility Features
CFexpress cards are available in three distinct form factors, each with precise physical dimensions to suit different device requirements while ensuring mechanical compatibility within the standard. Type A cards measure 20.0 mm in width, 28.0 mm in length, and 2.8 mm in thickness, with an approximate weight of 2 g.[38][39] Type B cards are larger at 38.5 mm × 29.8 mm × 3.8 mm and weigh about 7 g.[40][41] Type C cards, intended for higher-capacity applications, feature dimensions of 54.0 mm × 74.0 mm × 4.8 mm.[38] These form factors incorporate gold-fingered edge connectors that facilitate reliable PCIe signaling for high-speed data transfer, with the gold plating enhancing conductivity and durability against wear.[42] To prevent insertion errors across types, the cards employ mechanical keying through distinct notch positions on the connector edge, ensuring a Type A card, for example, cannot be inserted into a Type B slot due to mismatched physical profiles and pin configurations.[43] Industrial variants of CFexpress cards support an operating temperature range of -40°C to 85°C, enabling reliable performance in harsh environments such as professional video production outdoors.[44] Slot compatibility is maintained through CFA-defined connectors, which standardize the interface across devices, and adapters allow CFexpress Type B cards to function in XQD or CFast slots on firmware-upgradable cameras from manufacturers like Nikon and Canon.[5][45]| Form Factor | Dimensions (W × L × T, mm) | Approximate Weight (g) |
|---|---|---|
| Type A | 20.0 × 28.0 × 2.8 | 2 |
| Type B | 38.5 × 29.8 × 3.8 | 7 |
| Type C | 54.0 × 74.0 × 4.8 | - |
Comparisons and Compatibility
Relation to XQD and CFast
CFexpress Type B cards are physically and electrically compatible with the XQD format, sharing identical dimensions of 38.5 mm × 29.8 mm × 3.8 mm, which allows them to fit directly into XQD slots without adapters. This design choice by the CompactFlash Association (CFA) enables seamless integration, where firmware updates on compatible devices can unlock CFexpress functionality in existing XQD card slots. For instance, the Nikon D6 camera supports CFexpress Type B cards natively in its XQD slot, providing higher performance without hardware modifications.[15][40][46] In relation to CFast, CFexpress shares a common heritage under the CFA but represents a significant evolution by replacing the SATA interface—limited to around 600 MB/s—with the faster PCIe and NVMe protocols, enabling theoretical speeds up to 2 GB/s or more. Unlike CFexpress Type B and XQD, CFast cards (42 mm × 36.4 mm × 3.3 mm) lack direct physical compatibility due to differing form factors and connectors, positioning CFexpress as a conceptual successor for high-capacity, high-speed storage needs in professional applications.[9][47] The transition to CFexpress from XQD and CFast fosters a unified ecosystem within the CFA family of standards, reducing fragmentation and user confusion by consolidating high-performance options under a single, scalable protocol. The CFA's certification initiatives, including the release of the CFexpress 2.0 specification in 2019, supported hybrid compatibility testing and ensured reliable performance across legacy and new devices, streamlining adoption for manufacturers and end-users.[1][4]Differences from SD and Other Standards
CFexpress diverges significantly from Secure Digital (SD) standards in its architectural foundation, utilizing dedicated PCIe lanes—ranging from x1 for Type A cards to x2 for Type B and x4 for Type C—paired with the NVMe protocol to deliver full-bandwidth performance without the dual-mode constraints of SD Express. In contrast, SD Express (introduced in SD 7.0 and enhanced in SD 8.0) incorporates PCIe connectivity via additional pins but maintains backward compatibility with legacy UHS-I and UHS-II buses, effectively sharing the interface and limiting it to a maximum of x2 lanes even in the latest specification. This dedicated versus shared bus design allows CFexpress to prioritize uninterrupted high-throughput operations for professional workflows, while SD Express balances legacy support for broader consumer adoption.[48][49][1] Performance characteristics further highlight these gaps, with CFexpress achieving theoretical maximums of 4 GB/s in its 4.0 specification (PCIe 4.0 x2 for Type B) and offering superior sustained write speeds due to larger form factors that facilitate better thermal management through metal housings. SD Express, capped at 4 GB/s theoretical in SD 8.0 (PCIe 4.0 x2), often sees real-world limits closer to 2 GB/s in current implementations, constrained by its compact 32 mm × 24 mm × 2.1 mm size and plastic construction, which can lead to thermal throttling during prolonged high-speed transfers. CFexpress's larger dimensions—such as 38.5 mm × 29.8 mm × 3.8 mm for Type B—enable higher reliability in demanding scenarios like 8K video recording, though they reduce portability relative to SD's ubiquitous form.[48][49][1]| Aspect | CFexpress (Type B, 4.0) | SD Express (8.0) |
|---|---|---|
| PCIe Lanes | Dedicated x2 (up to x4 in Type C) | Up to x2 (shared with UHS) |
| Theoretical Max Speed | 4 GB/s (PCIe 4.0) | 4 GB/s (PCIe 4.0 x2) |
| Form Factor Size | 38.5 × 29.8 × 3.8 mm | 32 × 24 × 2.1 mm |
| Thermal Management | Metal housing for dissipation | Plastic; prone to throttling |