Read the analysis.
Find your perfect onsen.
Every onsen in Japan posts an analysis chart on its bathhouse wall — required by law, written only in Japanese. We decode each spring's pH, minerals, and bathing benefits so you can compare them and discover your perfect bath.
The wall poster, decoded for you.
Every onsen facility in Japan is required by the Hot Springs Act (1948) to display an analysis chart in the changing room — listing pH, temperature, minerals, and bathing benefits. Until now, this rich data was locked behind Japanese-only text. We translate the official numbers and explanations so you can choose your bath with confidence.
FAQWhat is an onsen analysis chart?
Five views of every onsen.
From a single analysis chart, we surface five complementary views — all translated.
Stimulation · Antibacterial · Skin Beauty · Heat Retention · Relaxation — computed from minerals and pH
From acidic to alkaline at a glance, with everyday comparisons
Cold spring to scalding — what to expect before you step in
Metasilicic acid, sodium chloride, sulfates — what each one does for your body
Strong astringent action that tightens skin. A key component of acidic springs, suited to oily or acne-prone skin.
The source of the distinctive sulfur smell. Dilates blood vessels via skin and inhalation to strongly boost circulation.
Mild antibacterial action keeps the skin clean. Trace transdermal absorption supports tooth and bone health.
Bathing and drinking benefits, plus warnings for sensitive skin
Three steps to your perfect bath.
Search on the map
Open the map, see hot springs near you, or filter by spring quality, pH, and temperature.
Open mapRead each analysis chart
Each onsen has a detail page with its analysis chart fully translated — radar, pH, temperature, minerals, indications.
Find your favorite onsen
Compare radars, minerals, and indications across springs to identify what suits you. Discover the bath that matches your preference.
10 official spring quality types.
Japan's hot springs are classified into 10 types under the Ministry of the Environment guidelines. Each carries a distinct character — from gentle simple springs to powerful acidic springs. Browse the catalogue and find the spring quality that matches your needs.
Built on official Japanese government data.
Every analysis chart you read here is rooted in Japanese law (Hot Springs Act, 1948) and the Ministry of the Environment's published guidelines. Spring type names, indications, and descriptions follow the Ministry's official multilingual notation manual.
- Hot Springs Act (Act No. 125 of 1948), Article 18↗
Japanese law requires every hot spring facility serving the public to display source name, spring type, temperature, mineral composition, and analysis date on-site.
https://laws.e-gov.go.jp/law/323AC0000000125 - Ministry of the Environment of Japan — Hot Springs Protection and Utilization↗
The Ministry oversees laws, notices, and guidelines for Japanese hot springs. All analysis data on this site originates from this regulatory framework.
https://www.env.go.jp/nature/onsen/docs/index.html - Mineral Spring Analysis Guidelines (2014 Revision)↗
All onsen analysis charts in Japan are issued by registered analysts following these official guidelines.
https://www.env.go.jp/nature/onsen/docs/shishin_bunseki.html - Multilingual Notation Manual for Hot Spring Areas (Ministry of the Environment)↗
Spring type names, indications, and descriptions on this site follow the official translations published by the Ministry of the Environment.
https://www.env.go.jp/nature/onsen/pdf/hyouki2021.pdf - OpenStreetMap (ODbL)↗
Location data for candidate hot springs (not yet registered with analysis charts) is contributed by OpenStreetMap contributors.
https://www.openstreetmap.org/copyright
Frequently asked questions
Find your next bath.
Browse the map or filter by minerals — all in your language, all from official data.