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# Expanded identity primitives \[Use any identity protocol alongside MPP]

`mppx` now lets any paid route check who's calling before it shows a price: a verified email, your own API keys, a [World ID](https://world.org/world-id)-verified human, or a protocol you write yourself. Explore the API interactively in the [MPP playground](https://mpp.dev/playground/identity).

## Identity alongside payments

MPP doesn't pick an identity provider for you. Identity runs next to the core payment flow, not inside it:

* **Bring any identity provider.** Use a built-in verifier, or wrap the auth you already run.
* **Check before the price.** Callers who don't pass get a standard unauthenticated HTTP response and never see payment terms.
* **Keep the core MPP flow.** Payments work the same with or without identity.

## Add identity to a service

Pass verifiers in a route's `identity` option, then read who passed from the result:

```ts twoslash [server.ts]
import type * as Identity from 'mppx/identity'
import { Mppx, tempo } from 'mppx/server'

declare const verifier: Identity.Verifier<{ email: string }>

const mppx = Mppx.create({
  methods: [tempo.charge({ testnet: true })],
})

export async function handler(request: Request) {
  // [!code hl:start]
  const result = await mppx.charge({
    amount: '0.05',
    identity: [verifier],
  })(request)
  // [!code hl:end]
  if (result.status === 402) return result.challenge

  const identity = result.identity?.get(verifier) // [!code hl]
  return result.withReceipt(Response.json(identity))
}
```

## Examples

:::code-group
```ts twoslash [Email]
import * as EmailOtp from 'mppx/extensions/identity/email-otp'
import { Mppx, tempo } from 'mppx/server'

// [!code hl:start]
const email = EmailOtp.Server.verifier({
  allow: (address) => address.endsWith('@example.com'),
  audience: 'https://api.example.com',
  issuer: 'https://identity.mpp.tempo.xyz',
})
// [!code hl:end]

const mppx = Mppx.create({
  methods: [tempo.charge({ testnet: true })],
})

export const handler = mppx.charge({
  amount: '0.05',
  identity: [email],
})
```

```ts twoslash [API keys]
import * as Identity from 'mppx/identity'
import { Mppx, tempo } from 'mppx/server'

declare const customers: ReadonlyMap<string, { customerId: string }>

// [!code hl:start]
const customer = Identity.from({
  challenge: { 'WWW-Authenticate': 'ApiKey' },
  verify(request) {
    const key = request.headers.get('X-Api-Key')
    if (!key) return undefined
    const identity = customers.get(key)
    if (!identity) throw new Identity.Rejection('Unknown API key.', { status: 'forbidden' })
    return identity
  },
})
// [!code hl:end]

const mppx = Mppx.create({
  methods: [tempo.charge({ testnet: true })],
})

export const handler = mppx.charge({
  amount: '0.05',
  identity: [customer],
})
```

```ts [World ID]
import * as World from 'mppx/extensions/identity/world'
import { Mppx, tempo } from 'mppx/server'

// [!code hl:start]
const human = World.Server.verifier({
  acr: [World.Constants.acr.orb],
  audience: 'https://api.example.com',
  issuer: 'https://world-id.issuer.example',
})
// [!code hl:end]

const mppx = Mppx.create({
  methods: [tempo.charge({ testnet: true })],
})

export const handler = mppx.charge({
  amount: '0.01',
  identity: [human],
})
```

```ts twoslash [Custom]
import { Mppx, tempo } from 'mppx/client'
import type * as Identity from 'mppx/identity'
import type { Account } from 'viem'

declare const account: Account
declare function signPartnerToken(request: Request): Promise<string>

// [!code hl:start]
const partner: Identity.Prover = {
  headers: ['x-partner-token'],
  async prove(request) {
    const headers = new Headers(request.headers)
    headers.set('X-Partner-Token', await signPartnerToken(request))
    return new Request(request, { headers })
  },
  scope: ['https://api.example.com'],
}
// [!code hl:end]

const client = Mppx.create({
  identity: [partner],
  methods: [tempo({ account })],
  polyfill: false,
})
```
:::

## Explore the MPP playground

Explore the API interactively in the [MPP playground](https://mpp.dev/playground/identity). Buy a haiku as an anonymous caller, with a verified email, or with an API key, and see how the price and the code change.

## Get started

* [Identity in MPP](/extensions/identity)
* [`Identity.from` reference](/sdk/typescript/core/Identity.from)
* [Email OTP example](https://github.com/wevm/mppx/tree/main/examples/email-otp)
* [World ID docs](https://docs.world.org/world-id)