Rainy Cafe plays a mix of rain sounds and cafe background noise, which is a combination that many people find helps them focus. You can adjust the volume of each independently, or mute one entirely. There's no music, no lyrics, no sudden changes — just a steady ambient backdrop. The site is simple to the point of being invisible, which is exactly what you want from a background noise tool.

It's free, requires no account, and works in any browser. There's also a timer if you want to work in focused blocks. For people who find complete silence distracting or who work in noisy environments, it's a small tool that makes a noticeable difference. Sometimes the simplest websites are the most useful.