Dial-up modems connected home computers to the internet through ordinary telephone lines, mainly in the 1990s and early 2000s before broadband became common. The handshake sound was the audible result of two modems testing the line and agreeing on a speed, so it became closely linked with waiting to get online. As broadband replaced dial-up, the noise survived as a cultural shorthand for the early internet, appearing in comedy sketches, retro edits and reaction videos whenever creators want an instant nineties reference.