The first computer "bug" was a real moth

On September 9, 1947, operators running the Harvard Mark II computer in Cambridge, Massachusetts traced a malfunction to a literal moth lodged between the contacts of a relay, physically blocking it from closing.

They removed the insect and taped it into the machine’s logbook, adding the wry note: “First actual case of bug being found.” That page, moth still attached, now lives in the Smithsonian’s National Museum of American History.

The word “bug” for a technical fault was already decades old — engineers had used it since the 1870s — so the team’s joke worked precisely because the term existed. The pioneering programmer Grace Hopper was present and made the story famous in later lectures, though historians say she probably didn’t write the note herself.

The episode didn’t coin “bug,” but it gave computing its most beloved origin myth — and a real specimen to prove it.