> ## Documentation Index
> Fetch the complete documentation index at: https://docs.authsignal.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Web SDK
> Learn how to use the Authsignal Web SDK.
The Authsignal Web SDK can be used to:
* Launch the pre-built UI to let users set up MFA and complete challenges
* Sign up and sign in users using passkeys or security keys
* Build custom UIs for authenticating with email OTP, SMS OTP, WhatsApp OTP, authenticator app, push, or QR code
## Installation
```bash npm theme={null}
npm install @authsignal/browser
```
```bash yarn theme={null}
yarn add @authsignal/browser
```
```bash pnpm theme={null}
pnpm add @authsignal/browser
```
```bash bun theme={null}
bun add @authsignal/browser
```
This will add our module to your `package.json`.
## Initialization
Initialize the client with your tenant ID and the API URL for your region.
```ts theme={null}
import { Authsignal } from "@authsignal/browser";
const authsignal = new Authsignal({
tenantId: "YOUR_TENANT_ID",
baseUrl: "YOUR_REGION_BASE_URL",
});
```
You can find your `tenantId` in the [Authsignal Portal](https://portal.authsignal.com/organisations/tenants/api).
You must specify the correct `baseUrl` for your tenant's region.
| Region | API URL |
| ------------- | ---------------------------------- |
| US (Oregon) | `https://api.authsignal.com/v1` |
| AU (Sydney) | `https://au.api.authsignal.com/v1` |
| EU (Ireland) | `https://eu.api.authsignal.com/v1` |
| CA (Montreal) | `https://ca.api.authsignal.com/v1` |
### Parameters
Your Authsignal tenant ID, found in the [Authsignal Portal](https://portal.authsignal.com/organisations/tenants/api).
The API URL for your tenant's region. See the [region table](#initialization) above.
A callback invoked when the current token expires. Use it to prompt the user to re-authenticate or to
fetch a fresh token.
The name of the cookie used to persist the anonymous device ID. Defaults to `__as_aid`.
The domain used when setting the anonymous device ID cookie. Defaults to the current
`location.hostname`.
Whether to log SDK warnings and errors to the console. Defaults to `false`.
## Usage