Alternative Airplay (formerly known as Modern Rock Tracks (1988–2009) and Alternative Songs (2009–2020)) is a music chart in the United States that has appeared in Billboard magazine since September 10, 1988. It ranks the 40 most-played songs on alternative and modern rock radio stations. Introduced as Modern Rock Tracks, the chart served as a companion to the Mainstream Rock chart (then called Album Rock Tracks), and its creation was prompted by the explosion of alternative music on American radio in the late 1980s. During the first several years of the chart, it regularly featured music that did not receive commercial radio airplay anywhere but on a few modern rock and college rock radio stations. This included many electronic and post-punk artists. Gradually, as alternative rock became more mainstream (spearheaded by the grunge explosion in the early 1990s), alternative and mainstream rock radio stations began playing many of the same songs. By the late 2000s, the genres became more fully differentiated with only limited crossover. The Alternative Airplay chart features more alternative rock, indie pop, and pop punk artists while the Mainstream Rock chart leans towards more guitar-tinged blues rock, hard rock, and heavy metal.
The chart is based solely on radio airplay ranked by a calculation of the total number of spins each song receives per week. As of 2012, approximately 80 alternative radio stations across the United States are electronically monitored 24 hours a day, seven days a week by Nielsen Broadcast Data Systems. The chart had 30 positions when it was introduced in September 1988 and expanded to 40 positions on September 10, 1994.
The chart was renamed to Alternative Songs beginning with the June 20, 2009, issue after Billboard fully absorbed Radio & Records, whose similar chart was called "Alternative" and to reflect the music industry's more common use of the term. In June 2020, Billboard introduced the separate Hot Alternative Songs chart, which uses similar methodology as the Billboard Hot 100 by measuring the popularity of songs classified as alternative across all radio formats, streaming services, and sales within the United States. To avoid confusion, Alternative Songs was renamed Alternative Airplay.