M-Systems, an Israeli company, were granted a US patent on November 14, 2000, titled "Architecture for a [USB]-based Flash Disk", and crediting the invention to Amir Ban, Dov Moran and Oron Ogdan, all M-Systems employees at the time. The patent application was filed by M-Systems in April 1999. Later in 1999, IBM filed an invention disclosure by one of its employees. Flash drives were sold initially by Trek 2000 International, a company in Singapore, which began selling in early 2000. IBM became the first to sell USB flash drives in the United States in 2000. The initial storage capacity of a flash drive was 8 MB. Another version of the flash drive, described as a pen drive, was also developed. Pua Khein-Seng from Malaysia has been credited with this invention. Patent disputes have arisen over the years, with competing companies including Singaporean company Trek Technology and Chinese company Netac Technology, attempting to enforce their patents. Trek won a suit in Singapore, but has lost battles in other countries. Netac Technology has brought lawsuits against PNY Technologies, Lenovo, aigo, Sony, and Taiwan's Acer and Tai Guen Enterprise Co.
Flash drives are often measured by the rate at which they transfer data. Transfer rates may be given in megabytes per second (MB/s), megabits per second (Mbit/s), or in optical drive multipliers such as "180X" (180 times 150 KiB/s). File transfer rates vary considerably among devices. Second generation flash drives have claimed to read at up to 30 MB/s and write at about half that rate, which was about 20 times faster than the theoretical transfer rate achievable by the previous model, USB 1.1, which is limited to 12 Mbit/s (1.5 MB/s) with accounted overhead. The effective transfer rate of a device is significantly affected by the data access pattern. 
By 2002, USB flash drives had USB 2.0 connectivity, which has 480 Mbit/s as the transfer rate upper bound; after accounting for the protocol overhead that translates to a 35 MB/s effective throughput. That same year, Intel sparked widespread use of second generation USB by including them within its laptops.
Third generation USB flash drives were announced in late 2008 and became available in 2010. USB 3.0 was slow to appear in laptops. As of 2010, the majority of laptop models still contained the 2.0.
Like USB 2.0 before it, USB 3.0 dramatically improved data transfer rates compared to its predecessor. The USB 3.0 interface specified transfer rates up to 5 Gbit/s (625 MB/s), compared to USB 2.0's 480 Mbit/s (60 MB/s). By 2010 the maximum available storage capacity for the devices had reached upwards of 128GB.
In January 2013, tech company Kingston, released a flash drive with 1TB of storage. The first USB 3.1 type-C flash drives, with read/write speeds of around 530 MB/s, were announced in March 2015. As of July 2016, flash drives within the 8 to 256 GB were sold more frequently than those between 512 GB and 1 TB units. In 2017, Kingston Technology announced the release of a 2-TB flash drive.
On a USB flash drive, one end of the device is fitted with a single Standard-A USB plug; some flash drives additionally offer a micro USB plug, facilitating data transfers between different devices.