> ## Documentation Index > Fetch the complete documentation index at: https://docs.userkit.dev/llms.txt > Use this file to discover all available pages before exploring further. # Sign in with an email code > Spends the code and signs the contact in. The code arrived in the inbox, so it proves the address exactly like a magic link does: the contact is marked identified, the address is marked verified, and the session it mints is verified. Every failure answers the same `invalid_code` — a wrong code, an expired or already-spent one, a challenge issued for another environment, and a challenge that never had a code behind it because the address has no account. Anything else would move the enumeration oracle here. Each code carries an attempt budget of 5. A guess costs one whether or not it was right, and the code is dead when the budget runs out: six digits is a million, which a rate limit alone does not close. With two-factor on, the answer is a `TwoFactorChallenge` instead of a session — the code is spent either way. Rate limited to 20 requests per 5 minutes per IP. ## OpenAPI ````yaml /api-reference/openapi.json post /v1/contact-auth/email-code/verify openapi: 3.1.0 info: title: UserKit API version: 1.0.0 description: >- The HTTP surface of UserKit. Two planes share one API. The **staff plane** is what a human uses in the panel: users, organizations, roles, members, keys. The **customer plane** is what a developer's own product uses: contacts, identities, hosted or federated sign-in. Every error answers the same envelope — `{"error": {"code", "message"}}`. The `code` is a stable contract to branch on; the `message` is for a person and may change. servers: - url: '{baseUrl}' description: The API host. variables: baseUrl: default: https://api.userkit.dev description: Base URL of the API, no trailing slash. security: - sessionToken: [] tags: - name: Authentication description: >- Public sign-up, sign-in, two-factor and password recovery for staff accounts. - name: Session description: >- The active session: who the caller is, which organization they are in, and signing out. - name: Account description: The caller's own account — profile, password, sessions, avatar. - name: Two-factor description: >- TOTP setup, activation and recovery codes. Returns 501 when two-factor is unavailable on the server. - name: Organizations description: The organizations a user belongs to, and the active one. - name: Environments description: >- The live and test environments seeded with every organization, and their identity settings. - name: Members description: Memberships and invitations. - name: Roles description: Roles and the permission catalogue they draw from. - name: API keys description: Secret keys (`uk_sk_…`) and publishable keys (`uk_pk_…`). - name: Contacts (panel) description: >- The staff view of the customer plane. Reads take `?environment=` as an explicit view parameter. - name: Contacts (server) description: >- The machine surface, authenticated by an API key. The environment is the key's environment and cannot be named by the caller. - name: Customer plane description: >- Called from the developer's own pages with a publishable key: boot, magic link, and the contact's own session. - name: Hosted auth description: >- Sign-up, sign-in, verification and recovery for contacts, when UserKit owns the account. - name: System description: Health and the internal job callback. paths: /v1/contact-auth/email-code/verify: post: tags: - Customer plane summary: Sign in with an email code description: >- Spends the code and signs the contact in. The code arrived in the inbox, so it proves the address exactly like a magic link does: the contact is marked identified, the address is marked verified, and the session it mints is verified. Every failure answers the same `invalid_code` — a wrong code, an expired or already-spent one, a challenge issued for another environment, and a challenge that never had a code behind it because the address has no account. Anything else would move the enumeration oracle here. Each code carries an attempt budget of 5. A guess costs one whether or not it was right, and the code is dead when the budget runs out: six digits is a million, which a rate limit alone does not close. With two-factor on, the answer is a `TwoFactorChallenge` instead of a session — the code is spent either way. Rate limited to 20 requests per 5 minutes per IP. operationId: verifyEmailCode requestBody: required: true content: application/json: schema: type: object required: - publishable_key - challenge_token - code properties: publishable_key: type: string challenge_token: type: string example: uk_ec_… code: type: string description: The six digits from the email. example: '418902' responses: '200': description: Signed in, or stopped at the second factor. content: application/json: schema: oneOf: - type: object properties: contact: $ref: '#/components/schemas/Contact' token: type: string description: Contact session token, `uk_ct_…`. expires_at: type: string format: date-time verified: type: boolean - $ref: '#/components/schemas/TwoFactorChallenge' '401': description: >- `invalid_code` — wrong, expired, already spent, out of attempts, or for another environment. One answer for all of them. content: application/json: schema: $ref: '#/components/schemas/Error' '403': $ref: '#/components/responses/OriginNotAllowed' '429': $ref: '#/components/responses/RateLimited' security: [] components: schemas: Contact: type: object description: One of the developer's own users — anonymous or identified. properties: id: type: string format: uuid name: type: - string - 'null' email: type: - string - 'null' avatar_url: type: - string - 'null' identified: type: boolean description: Whether this contact is more than a visitor. email_verified: type: boolean description: >- Whether the ADDRESS was proven — by a verification link, a reset link or a magic link. Distinct from a session's `verified` flag. attribution: $ref: '#/components/schemas/Attribution' first_seen_at: type: string format: date-time last_seen_at: type: string format: date-time created_at: type: string format: date-time TwoFactorChallenge: type: object description: >- The password step succeeded and the account has two-factor on. Exchange the challenge at `/v1/auth/two-factor` within 5 minutes. This token is not a session and carries its own prefix precisely so it can never be used as one. properties: two_factor_required: type: boolean const: true challenge_token: type: string description: '`uk_2fa_…`.' Error: type: object description: Every error in this API answers this envelope. properties: error: type: object properties: code: type: string description: Stable. Branch on this. message: type: string description: For a person. May change. required: - code - message required: - error example: error: code: forbidden message: your role does not allow this action Attribution: type: object description: >- First touch, captured on the visitor at first load and preserved through a merge. All fields optional; empty means unknown. properties: utm_source: type: - string - 'null' utm_medium: type: - string - 'null' utm_campaign: type: - string - 'null' utm_term: type: - string - 'null' utm_content: type: - string - 'null' referrer: type: - string - 'null' landing_page: type: - string - 'null' responses: OriginNotAllowed: description: >- `origin_not_allowed` — this publishable key does not accept calls from this origin. content: application/json: schema: $ref: '#/components/schemas/Error' RateLimited: description: >- `rate_limited` — too many requests. `Retry-After` carries the window in seconds. The counters are shared across instances. When that store cannot be reached each instance counts on its own instead: the limits get looser, never absent. headers: Retry-After: schema: type: integer description: Seconds until the window resets. content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: sessionToken: type: http scheme: bearer description: >- A staff session token, `uk_st_…`. Minted by sign-up, sign-in or the two-factor exchange. ````