Choose a provider

Pick an SMS provider for SMS SDK: a quick decision table, support status, capability matrix, and sender types for Twilio, Telnyx, Plivo, Vonage, Bandwidth, and Sinch.

Every adapter uses the same send() call and the same webhook events, so you can pick by features and switch later. Start with the provider where your numbers and sender registrations already live.

Which one should I pick?

Your situation	Use
You already have an account and registered senders somewhere	That provider
You need MMS	Twilio, Telnyx, or Plivo
You need short codes	Twilio, Telnyx, Plivo, Bandwidth, or Sinch
You need scheduled sends from any sender	Telnyx or Sinch
You need scheduling from a Twilio Messaging Service	Twilio
You want fallback to trigger on exactly the right errors	Twilio or Telnyx. Their error codes are fully documented.
You use the Vonage Messages API	Vonage, with JWT auth if you need webhooks
You want a second provider for fallback	Any two. Put a Supported one first if you mix statuses. See Fallback and retries.

Support status

Provider	API	Status	Main limits
Twilio	Programmable Messaging, `2010-04-01`	Supported	None
Telnyx	Messaging API v2	Supported	None
Plivo	Message API v1	Partial	Plivo does not document its error body, so 4xx responses other than 401 and 429 are `request` and never fall back.
Vonage	Messages API v1, channel `sms`	Partial	Error classification is inferred. No short codes, no MMS. Basic auth gets no webhooks.
Bandwidth	Messaging API v2	Partial	SMS only. Callbacks are unsigned and checked with Basic credentials. Errors classified by HTTP status; a 429 counts as a rate limit only with a Bandwidth error body.
Sinch	SMS API (`/xms/v1`)	Partial	No MMS. HMAC callback format is unpublished; Basic is the documented option. Few error codes classified.

Supported adapters build requests, responses, error mapping, and webhooks from official documentation and pass the adapter contract tests. Partial adapters pass the same tests, but some provider behavior could not be confirmed from official documentation. Each provider page lists the gaps. Read the status at runtime from adapter.support or sms.capabilities().

None of the providers documents send idempotency for SMS, so no adapter has native idempotency. See Prevent duplicate sends.

Capabilities

	Twilio	Telnyx	Plivo	Vonage (JWT)	Vonage (Basic)	Bandwidth	Sinch
MMS (`mediaUrls`)	✅ max 10	✅	✅	❌	❌	❌	❌
Scheduling (`sendAt`)	✅ Messaging Service only	✅	❌	❌	❌	❌	✅
Validity period (`validityPeriodSec`)	1 to 36,000 s	❌	5 to 10,799 s	20 to 604,800 s	20 to 604,800 s	❌	1 to 2,592,000 s
Per-message `webhookUrl`	✅	✅	✅	✅	❌	❌	✅
Delivery status webhooks	✅	✅	✅	✅	❌	✅	✅
Inbound webhooks	✅	✅	✅	✅	❌	✅	✅
STOP/HELP detection	✅ provider `OptOutType`	Keyword	Keyword	Keyword	❌	Keyword	Keyword
Webhook replay window	None	300 s	None	300 s	n/a	None	300 s with HMAC, none with Basic

Every adapter sends text. An unsupported field throws UnsupportedFieldError before any request, so nothing is sent. “Keyword” means SMS SDK detects STOP and HELP in the message text; Twilio also reports its own opt-out signal. Without a replay window, store each event’s dedupeKey and skip repeats, as covered in Webhook security.

Sender types

Sender	Twilio	Telnyx	Plivo	Vonage	Bandwidth	Sinch
Long code	✅	✅	✅	✅	✅	✅
Toll-free	✅	✅	✅	✅	✅	✅
Short code	✅	✅	✅	❌	✅	✅
Alphanumeric sender ID	✅	✅ needs `messagingProfileId`	✅	✅	❌	✅
`{ messagingService }`	Messaging Service SID	Messaging profile ID	Powerpack UUID	❌	❌	❌

This table says what the adapter can send from. The provider and the carriers decide whether your account may use that sender in a given country. Each provider page lists its rules under Senders, and Registration and consent covers 10DLC, toll-free verification, short codes, and sender IDs.

Switching providers

Changing the adapter is one line of code. The account work takes longer: senders and their registrations belong to one provider account, and you need new webhook URLs and credentials. See Switch providers for the checklist.

For a provider that is not listed, see Build your own adapter.