> ## Documentation Index
> Fetch the complete documentation index at: https://docs.neus.network/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

> How servers and apps authenticate to the NEUS API.

Pick the path that matches your caller. Most products use Hosted Verify for people and a profile access key for servers.

Credits apply to checks and saved results, not to hosted session sign-in. See [Trust stack](../platform/trust-stack) · [Pricing](../platform/pricing).

| Need                                         | Mechanism                                    | Wallet code in your app |
| -------------------------------------------- | -------------------------------------------- | ----------------------- |
| Sign-in for your app                         | Hosted Verify + `intent=login` + `returnUrl` | No                      |
| Access or checkout (default)                 | `VerifyGate` / Hosted Verify + `gateId`      | No                      |
| MCP client sign-in                           | OAuth 2.0 + PKCE                             | No                      |
| Server automation as your profile            | Bearer `npk_*` access key                    | No                      |
| Server creates receipts for an approved user | App link + `verifyFromApp`                   | No                      |
| Sign inside your page                        | SDK `verify` + `wallet`                      | Yes — rare              |

Server integration: [Integrations](../cookbook/integrations).

## Hosted Verify (default)

`https://neus.network/verify` — [Hosted Verify](../cookbook/auth-hosted-verify).

Send users to your checkout with `gateId`; the enforcement policy bills your Hub credits.

## MCP OAuth

MCP clients (Claude Code, OpenAI, VS Code, Cursor) authenticate via **OAuth 2.0 Authorization Code with PKCE**:

```bash theme={"dark"}
neus setup
neus auth
```

See [MCP OAuth](../mcp/oauth).

## Profile access keys

[Access keys](https://neus.network/profile?tab=account) for servers, CI, and MCP automation. Never in browser bundles.

## Backend receipts

For backend-created receipts after a user approves your product once, see [Integrations](../cookbook/integrations). Separate from creating a **portal** under profile → **Portals**, which bills hosted checks to your account.

## Signing inside your app

[Signing format](../verification/signing-format) · `signMessage` from `@neus/sdk`

## Raw HTTP

`POST /api/v1/verification/standardize` → sign `signerString` → `POST /api/v1/verification`. [Signing format](../verification/signing-format).

[MCP Auth](../mcp/auth) · [SDK Authentication](../sdks/authentication)