twilio

by vercel

Emulated Twilio REST APIs for local development and testing. Use when the user needs to test Twilio Messaging, Verify, Voice, phone numbers, webhooks, status…

npx skills add https://github.com/vercel-labs/emulate --skill twilio

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Twilio API Emulator

Stateful Twilio REST emulation with seeded accounts, Auth Tokens, API keys, incoming phone numbers, Programmable Messaging, Messaging Services, Verify, basic Voice calls, Conversations REST resources, signed webhooks, local simulator routes, and an inspector.

Start

npx emulate --service twilio

Default URL: http://localhost:4013 when all services are started, or http://localhost:4000 when Twilio is the only service.

Defaults

TWILIO_ACCOUNT_SID=AC00000000000000000000000000000000
TWILIO_AUTH_TOKEN=twilio_test_auth_token
TWILIO_API_KEY=SK00000000000000000000000000000000
TWILIO_API_SECRET=twilio_test_api_secret
TWILIO_PHONE_NUMBER=+15551234567
TWILIO_VERIFY_SERVICE_SID=VA00000000000000000000000000000000

URL Mapping

Real Twilio URL	Emulator URL
`https://api.twilio.com/2010-04-01/...`	`$TWILIO_EMULATOR_URL/2010-04-01/...`
`https://messaging.twilio.com/v1/...`	`$TWILIO_EMULATOR_URL/messaging/v1/...`
`https://verify.twilio.com/v2/...`	`$TWILIO_EMULATOR_URL/verify/v2/...`

The official Node SDK builds absolute Twilio product URLs. In SDK tests, use a custom request client that rewrites those hosts to the emulator prefixes above.

Auth

HTTP Basic auth accepts either:

Account SID and Auth Token
API Key SID and API Key Secret

Core Routes

POST /2010-04-01/Accounts/{AccountSid}/Messages.json - create outbound message
GET /2010-04-01/Accounts/{AccountSid}/Messages.json - list messages
POST /2010-04-01/Accounts/{AccountSid}/Calls.json - create outbound call
POST /verify/v2/Services/{ServiceSid}/Verifications - start verification
POST /verify/v2/Services/{ServiceSid}/VerificationCheck - check verification code
POST /conversations/v1/Services/{ServiceSid}/Conversations - create Conversation
POST /conversations/v1/Services/{ServiceSid}/Conversations/{ConversationSid}/Participants - add participant
POST /conversations/v1/Services/{ServiceSid}/Conversations/{ConversationSid}/Messages - add message
POST /_twilio/simulate/inbound-message - simulate inbound SMS
POST /_twilio/simulate/message-status - simulate message status callback
POST /_twilio/simulate/inbound-call - simulate inbound call

SMS And OTP Testing

The seeded Verify Service code is 123456.
Use CustomCode when creating a Verification to force a per-verification code.
Use GET /_twilio/simulate/verification-code?To=...&ServiceSid=... with Basic auth to fetch the latest local code for an E2E test.
Use POST /_twilio/simulate/verification-status with VerificationSid or To to force local Verify state.
Use POST /_twilio/simulate/inbound-message to test inbound SMS webhooks.
Inbound SMS uses an assigned Messaging Service inbound_request_url before falling back to the phone number sms_url.
Use POST /_twilio/simulate/message-status to test outbound status callbacks.

Current Limits

No real SMS, MMS, WhatsApp, email, voice, carrier, compliance, billing, SendGrid, Studio, Flex, TaskRouter, Video, Sync, Segment, Conversations SDK websocket behavior, or complete TwiML interpreter behavior is implemented.