Reel-to-reel audio tape recording, also called open-reel recording, is magnetic tape audio recording in which the recording tape is spooled between reels. To prepare for use, the supply reel (or feed reel) containing the tape is placed on a spindle or hub. The end of the tape is manually pulled from the reel, threaded through mechanical guides and over a tape head assembly, and attached by friction to the hub of the second, initially empty takeup reel. Reel-to-reel systems use tape that is 1⁄4, 1⁄2, 1, or 2 inches (6.35, 12.70, 25.40, or 50.80 mm) wide, which normally moves at 3+3⁄4, 7+1⁄2, 15 or 30 inches per second (9.525, 19.05, 38.10 or 76.20 cm/s).
Reel-to-reel preceded the development of the compact cassette with its tape 0.15 inches (3.8 mm) wide moving at 1+7⁄8 inches per second (4.8 cm/s). By writing the same audio signal across more tape, reel-to-reel systems give much greater fidelity at the cost of much larger tapes. In spite of the relative inconvenience and generally more expensive media, reel-to-reel systems developed in the early 1940s remained popular in audiophile settings into the 1980s and have re-established a specialist niche in the 21st century.