Which frontend SDK do you use?
supertokens-auth-react
supertokens-web-js / mobile
Share sessions across sub domains
Sharing sessions across multiple sub domains in SuperTokens can be configured by setting the sessionScope attribute of the Session recipe in your frontend code.
Example:
- Your app has two subdomains 
abc.example.comandxyz.example.com. We assume that the user logs in viaexample.com - To enable sharing sessions across 
example.com,abc.example.comandxyz.example.comthesessionsScopeattribute must be set to.example.com 
- ReactJS
 - Angular
 - Vue
 
import SuperTokens from "supertokens-auth-react";import Session from "supertokens-auth-react/recipe/session";
SuperTokens.init({    appInfo: {        // ...        // this should be equal to the domain where the user will see the login UI        apiDomain: "...",        appName: "...",        websiteDomain: "https://example.com"    },    recipeList: [        Session.init({            sessionScope: ".example.com"        })    ]});important
Session recipe config changes need to be reflected in both supertokens-auth-react and supertokens-web-js configs.
/app/auth/supertokensAuthComponent.tsx
import SuperTokens from "supertokens-auth-react";import Session from "supertokens-auth-react/recipe/session";
SuperTokens.init({    appInfo: {        // ...        // this should be equal to the domain where the user will see the login UI        apiDomain: "...",        appName: "...",        websiteDomain: "https://example.com"    },    recipeList: [        Session.init({            sessionScope: ".example.com"        })    ]});/app/app.component.ts
import SuperTokens from "supertokens-web-js";import Session from "supertokens-web-js/recipe/session";
SuperTokens.init({    appInfo: {        apiDomain: "...",        appName: "...",    },    recipeList: [        Session.init({            sessionScope: ".example.com"        }),    ],})important
Session recipe config changes need to be reflected in both supertokens-auth-react and supertokens-web-js configs.
/components/Supertokens.tsx
import SuperTokens from "supertokens-auth-react";import Session from "supertokens-auth-react/recipe/session";
SuperTokens.init({    appInfo: {        // ...        // this should be equal to the domain where the user will see the login UI        apiDomain: "...",        appName: "...",        websiteDomain: "https://example.com"    },    recipeList: [        Session.init({            sessionScope: ".example.com"        })    ]});/main.ts
import SuperTokens from "supertokens-web-js";import Session from "supertokens-web-js/recipe/session";
SuperTokens.init({    appInfo: {        apiDomain: "...",        appName: "...",    },    recipeList: [        Session.init({            sessionScope: ".example.com"        }),    ],})caution
Do not set sessionScope to a value that's in the public suffix list (Search for your value without the leading dot). Otherwise session management will not work.