Sento vs Onsen: What's the Difference?

With October 10th marking Sento Day (銭湯の日), it's a good time to look at a question many visitors and newcomers to Japan ask: what's the difference between a sento and an onsen?

The main difference is the water. An onsen uses naturally occurring hot spring water that comes from underground and meets specific mineral or temperature requirements. A sento, on the other hand, is a public bathhouse that typically uses heated tap water.

Historically, sento played an important role in Japanese communities. Before private bathrooms became common, local residents would visit their neighborhood bathhouse to wash, soak, and catch up with friends and neighbors. Many sento still operate today, offering an affordable and nostalgic glimpse into everyday Japanese life.

Onsen are often associated with travel and relaxation, particularly in mountain resorts, coastal towns, and other areas blessed with natural hot springs. Many feature scenic outdoor baths where visitors can enjoy the surrounding landscape while soaking.

The distinction isn't always obvious, however. Some modern bath facilities combine both types of baths under one roof. Whether you choose a sento or an onsen, both offer a chance to experience one of Japan's most cherished traditions: unwinding in a hot bath.