Common Swifts are easily noticeable, as they often stay in flocks and emit loud "swee-ree" "swee-ree" calls in flight. In appearance, a swift may resemble a swallow or a house martin, but the swift is larger than them and has a dark underside, whereas swallows and martins have white bellies. The swift has longer, sickle-shaped wings compared to a swallow or a martin.

The swift spends most of its time in flight – it can feed, collect material for its nest, mate, and even sleep while on the wing. Swifts begin nesting at the age of four and form lifelong pairs, which can last for more than 20 years, although data suggests that the average lifespan of this bird is significantly shorter. Most often, swifts nest in various crevices in buildings, but they can also use bird boxes and tree cavities. A swift's clutch contains 1 to 3 white eggs. There is one brood per year.
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