Vercel API Emulator

Fully stateful Vercel REST API emulation with Vercel-style JSON responses and cursor-based pagination.

Start

# Vercel only
npx emulate --service vercel

# Default port
# http://localhost:4000

Or programmatically:

import { createEmulator } from 'emulate'

const vercel = await createEmulator({ service: 'vercel', port: 4000 })
// vercel.url === 'http://localhost:4000'

Auth

Pass tokens as Authorization: Bearer <token>. All endpoints accept teamId or slug query params for team scoping.

curl http://localhost:4000/v2/user \
  -H "Authorization: Bearer test_token_admin"

Team-scoped requests resolve the account from the teamId or slug query parameter. User-scoped requests resolve the account from the authenticated user.

Pointing Your App at the Emulator

Environment Variable

VERCEL_EMULATOR_URL=http://localhost:4000

Vercel SDK / Custom Fetch

const VERCEL_API = process.env.VERCEL_EMULATOR_URL ?? 'https://api.vercel.com'

const res = await fetch(`${VERCEL_API}/v10/projects`, {
  headers: { Authorization: `Bearer ${token}` },
})

OAuth URL Mapping

Auth.js / NextAuth.js

{
  id: 'vercel',
  name: 'Vercel',
  type: 'oauth',
  authorization: {
    url: `${process.env.VERCEL_EMULATOR_URL}/oauth/authorize`,
  },
  token: {
    url: `${process.env.VERCEL_EMULATOR_URL}/login/oauth/token`,
  },
  userinfo: {
    url: `${process.env.VERCEL_EMULATOR_URL}/login/oauth/userinfo`,
  },
  clientId: process.env.VERCEL_CLIENT_ID,
  clientSecret: process.env.VERCEL_CLIENT_SECRET,
  profile(profile) {
    return {
      id: profile.sub,
      name: profile.name,
      email: profile.email,
      image: profile.picture,
    }
  },
}

Seed Config

tokens:
  test_token_admin:
    login: admin
    scopes: []

vercel:
  users:
    - username: developer
      name: Developer
      email: dev@example.com
  teams:
    - slug: my-team
      name: My Team
      description: Engineering team
  projects:
    - name: my-app
      team: my-team
      framework: nextjs
      buildCommand: next build
      outputDirectory: .next
      rootDirectory: null
      nodeVersion: "20.x"
      envVars:
        - key: DATABASE_URL
          value: postgres://localhost/mydb
          type: encrypted
          target: [production, preview]
  integrations:
    - client_id: oac_abc123
      client_secret: secret_abc123
      name: My Vercel App
      redirect_uris:
        - http://localhost:3000/api/auth/callback/vercel

Pagination

Cursor-based pagination using limit, since, and until query params. Responses include a pagination object:

curl "http://localhost:4000/v10/projects?limit=10" \
  -H "Authorization: Bearer $TOKEN"

API Endpoints

User & Teams

# Registration check
curl http://localhost:4000/registration

# Authenticated user
curl http://localhost:4000/v2/user -H "Authorization: Bearer $TOKEN"

# Update user
curl -X PATCH http://localhost:4000/v2/user \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "New Name", "email": "new@example.com"}'

# List teams (cursor paginated)
curl http://localhost:4000/v2/teams -H "Authorization: Bearer $TOKEN"

# Get team (by ID or slug)
curl http://localhost:4000/v2/teams/my-team -H "Authorization: Bearer $TOKEN"

# Create team
curl -X POST http://localhost:4000/v2/teams \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"slug": "new-team", "name": "New Team"}'

# Update team (name, slug, description)
curl -X PATCH http://localhost:4000/v2/teams/my-team \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "Updated Team", "description": "New description"}'

# List members
curl http://localhost:4000/v2/teams/my-team/members -H "Authorization: Bearer $TOKEN"

# Add member (by uid or email, with role)
curl -X POST "http://localhost:4000/v2/teams/team_id/members" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"email": "dev@example.com", "role": "MEMBER"}'

Roles: OWNER, MEMBER, DEVELOPER, VIEWER.

Projects

# Create project (with optional env vars, git, and build config)
curl -X POST http://localhost:4000/v11/projects \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "my-app", "framework": "nextjs", "buildCommand": "next build", "outputDirectory": ".next", "nodeVersion": "20.x", "environmentVariables": [{"key": "API_KEY", "value": "secret", "type": "encrypted", "target": ["production"]}]}'

# List projects (search, cursor pagination)
curl "http://localhost:4000/v10/projects?search=my-app" \
  -H "Authorization: Bearer $TOKEN"

# Get project (includes env vars)
curl http://localhost:4000/v9/projects/my-app \
  -H "Authorization: Bearer $TOKEN"

# Update project (framework, buildCommand, devCommand, installCommand,
#   outputDirectory, rootDirectory, nodeVersion, serverlessFunctionRegion,
#   publicSource, autoAssignCustomDomains, gitForkProtection,
#   commandForIgnoringBuildStep)
curl -X PATCH http://localhost:4000/v9/projects/my-app \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"framework": "remix"}'

# Delete project (cascades deployments, domains, env vars, protection bypasses)
curl -X DELETE http://localhost:4000/v9/projects/my-app \
  -H "Authorization: Bearer $TOKEN"

# Promote aliases status
curl http://localhost:4000/v1/projects/my-app/promote/aliases \
  -H "Authorization: Bearer $TOKEN"

# Protection bypass: generate, revoke, regenerate
curl -X PATCH http://localhost:4000/v1/projects/my-app/protection-bypass \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"generate": {"note": "CI preview", "scope": "deployment"}}'

# Revoke protection bypass secrets
curl -X PATCH http://localhost:4000/v1/projects/my-app/protection-bypass \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"revoke": ["secret_to_revoke"]}'

# Regenerate protection bypass secrets
curl -X PATCH http://localhost:4000/v1/projects/my-app/protection-bypass \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"regenerate": ["old_secret"]}'

Deployments

# Create deployment (auto-transitions to READY)
curl -X POST http://localhost:4000/v13/deployments \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "my-app", "target": "production", "meta": {"commit": "abc123"}, "regions": ["iad1"], "gitSource": {"type": "github", "ref": "main", "sha": "abc123", "repoId": "123", "org": "my-org", "repo": "my-app", "message": "Deploy", "authorName": "dev", "commitAuthorName": "dev"}}'

# Targets: "production", "preview", "staging"

# Get deployment (by ID or URL)
curl http://localhost:4000/v13/deployments/dpl_abc123 \
  -H "Authorization: Bearer $TOKEN"

# List deployments (filter by projectId, app, target, state; cursor paginated)
curl "http://localhost:4000/v6/deployments?projectId=my-app&target=production&limit=10" \
  -H "Authorization: Bearer $TOKEN"

# List deployments (filter by commit SHA)
curl "http://localhost:4000/v7/deployments?sha=abc123" \
  -H "Authorization: Bearer $TOKEN"

# Delete deployment
curl -X DELETE http://localhost:4000/v13/deployments/dpl_abc123 \
  -H "Authorization: Bearer $TOKEN"

# Cancel building deployment
curl -X PATCH http://localhost:4000/v12/deployments/dpl_abc123/cancel \
  -H "Authorization: Bearer $TOKEN"

# List deployment aliases
curl http://localhost:4000/v2/deployments/dpl_abc123/aliases \
  -H "Authorization: Bearer $TOKEN"

# Get build events/logs (supports direction, limit)
curl "http://localhost:4000/v3/deployments/dpl_abc123/events?direction=forward&limit=50" \
  -H "Authorization: Bearer $TOKEN"

# List deployment files
curl http://localhost:4000/v6/deployments/dpl_abc123/files \
  -H "Authorization: Bearer $TOKEN"

# Upload file (by SHA digest)
curl -X POST http://localhost:4000/v2/files \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/octet-stream" \
  -H "x-vercel-digest: sha256hash" \
  --data-binary @file.txt

Domains

# Add domain (with optional redirect, gitBranch, customEnvironmentId)
curl -X POST http://localhost:4000/v10/projects/my-app/domains \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "example.com", "redirect": null, "redirectStatusCode": null, "gitBranch": null}'

# *.vercel.app domains are auto-verified

# List domains (cursor paginated)
curl http://localhost:4000/v9/projects/my-app/domains \
  -H "Authorization: Bearer $TOKEN"

# Get, update, remove domain
curl http://localhost:4000/v9/projects/my-app/domains/example.com \
  -H "Authorization: Bearer $TOKEN"

# Verify domain
curl -X POST http://localhost:4000/v9/projects/my-app/domains/example.com/verify \
  -H "Authorization: Bearer $TOKEN"

Redirect status codes: 301, 302, 307, 308.

Environment Variables

# List env vars (with decrypt option; filter by gitBranch, customEnvironmentId)
curl "http://localhost:4000/v10/projects/my-app/env?decrypt=true" \
  -H "Authorization: Bearer $TOKEN"

# Create env vars (single, batch, or upsert)
curl -X POST "http://localhost:4000/v10/projects/my-app/env?upsert=true" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"key": "API_KEY", "value": "secret123", "type": "encrypted", "target": ["production", "preview"], "comment": "API key for service"}'

# Get env var
curl http://localhost:4000/v10/projects/my-app/env/env_abc123 \
  -H "Authorization: Bearer $TOKEN"

# Update env var
curl -X PATCH http://localhost:4000/v9/projects/my-app/env/env_abc123 \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"value": "newsecret"}'

# Delete env var
curl -X DELETE http://localhost:4000/v9/projects/my-app/env/env_abc123 \
  -H "Authorization: Bearer $TOKEN"

Env var types: system, encrypted, plain, secret, sensitive.

Blob

Implements the Vercel Blob API used by the @vercel/blob SDK (put, head, list, del). Point the SDK at the emulator with two environment variables:

VERCEL_BLOB_API_URL=http://localhost:4000/api/blob
BLOB_READ_WRITE_TOKEN=vercel_blob_rw_mystore_secret

Any token of the form vercel_blob_rw_<storeId>_<secret> is accepted; the store id is parsed from the token.

import { put, head, list, del } from '@vercel/blob'

const blob = await put('avatars/user.png', data, { access: 'public' })
// blob.url serves the bytes from the emulator
await head(blob.url)
await list({ prefix: 'avatars/' })
await del(blob.url)

Direct HTTP:

BLOB_TOKEN="vercel_blob_rw_mystore_secret"

# Upload (honors x-add-random-suffix, x-allow-overwrite, x-content-type,
#   x-cache-control-max-age, x-if-match headers)
curl -X PUT "http://localhost:4000/api/blob?pathname=docs/readme.txt" \
  -H "Authorization: Bearer $BLOB_TOKEN" \
  --data-binary @readme.txt

# Metadata (head)
curl "http://localhost:4000/api/blob?url=docs/readme.txt" \
  -H "Authorization: Bearer $BLOB_TOKEN"

# List (prefix, limit, cursor, mode=folded)
curl "http://localhost:4000/api/blob?prefix=docs/" \
  -H "Authorization: Bearer $BLOB_TOKEN"

# Delete
curl -X POST http://localhost:4000/api/blob/delete \
  -H "Authorization: Bearer $BLOB_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"urls": ["docs/readme.txt"]}'

# Serve content (public, no auth; ?download=1 forces attachment)
curl http://localhost:4000/blob/mystore/docs/readme.txt

Multipart uploads and client (browser) uploads are not supported yet.

API Keys

# Create API key (optional teamId scope)
curl -X POST "http://localhost:4000/v1/api-keys?teamId=team_abc123" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "CI Deploy Key"}'

# List API keys (optional teamId filter)
curl "http://localhost:4000/v1/api-keys?teamId=team_abc123" \
  -H "Authorization: Bearer $TOKEN"

# Delete API key
curl -X DELETE http://localhost:4000/v1/api-keys/ak_abc123 \
  -H "Authorization: Bearer $TOKEN"

Created API keys are automatically registered in the token map and can be used as Bearer tokens for all endpoints.

OAuth / Integrations

# Authorize (browser flow, shows user picker)
# GET /oauth/authorize?client_id=...&redirect_uri=...&scope=...&state=...

# Token exchange (supports PKCE; accepts JSON or form-urlencoded)
curl -X POST http://localhost:4000/login/oauth/token \
  -H "Content-Type: application/json" \
  -d '{"client_id": "oac_abc123", "client_secret": "secret_abc123", "code": "<code>", "redirect_uri": "http://localhost:3000/api/auth/callback/vercel"}'

# User info (returns sub, email, email_verified, name, preferred_username, picture)
curl http://localhost:4000/login/oauth/userinfo \
  -H "Authorization: Bearer $TOKEN"

Common Patterns

Create Project and Deploy

TOKEN="test_token_admin"
BASE="http://localhost:4000"

# Create project
curl -X POST $BASE/v11/projects \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "my-app", "framework": "nextjs"}'

# Add env var
curl -X POST $BASE/v10/projects/my-app/env \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"key": "DATABASE_URL", "value": "postgres://...", "type": "encrypted", "target": ["production"]}'

# Create deployment
curl -X POST $BASE/v13/deployments \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "my-app", "target": "production"}'

OAuth Integration Flow

1. Redirect user to $VERCEL_EMULATOR_URL/oauth/authorize?client_id=...&redirect_uri=...&state=...
2. User picks a seeded user on the emulator's UI
3. Emulator redirects back with ?code=...&state=...
4. Exchange code for token via POST /login/oauth/token
5. Fetch user info via GET /login/oauth/userinfo

PKCE is supported. Pass code_challenge and code_challenge_method on authorize, then code_verifier on token exchange.

Team-Scoped Requests

All endpoints accept teamId or slug query params:

curl "http://localhost:4000/v10/projects?teamId=team_abc123" \
  -H "Authorization: Bearer $TOKEN"

curl "http://localhost:4000/v10/projects?slug=my-team" \
  -H "Authorization: Bearer $TOKEN"

Custom emulators alongside built-ins

Use npx emulate init --custom inventory to scaffold a third-party API emulator and test. Register it in emulate.config.ts with defineConfig from emulate, alongside built-in entries such as { emulator: "vercel" }. Run npx emulate start --watch to reload imports and inspect custom state at the printed /_emulate URL. Successful reloads reset the run to seed. Existing flat seed configs still work; --config selects an explicit file. For authoring and testing third-party API emulators, see https://emulate.dev/docs/custom-emulators.