How to migrate from Vonage to Sinch

Both Vonage and Sinch are publicly traded cloud communications platforms that expose SMS, voice, and multichannel messaging through REST APIs — Vonage out of Holmdel, USA (part of Ericsson), and Sinch out of Stockholm, Sweden. On the messaging.dev Score, Vonage rates 89/100 and Sinch 92/100. The gap is small, so this guide focuses on the concrete API and capability changes you make when moving from one to the other rather than on which is “better.”

What changes when you move

Channels. You keep every channel you already use: SMS, MMS, RCS, WhatsApp, Viber, Facebook Messenger, and Voice are supported on both platforms. You also gain three channels Vonage does not list — Telegram, Apple Messages for Business, and Email. No channel is lost in the move.

Compliance and data residency are effectively a wash. Both carry GDPR, ISO 27001, SOC 2, and HIPAA alignment, and both offer US and EU servers with data-residency choice. Sinch additionally lists Brazil among its other regions; otherwise the two match.

SDKs. Both ship official SDKs for Node.js, Python, PHP, Java, and C#. Vonage also offers Ruby and Kotlin, which Sinch does not — if your code depends on those, plan a REST path. Both provide a sandbox and both rate high on docs quality. Sinch additionally exposes SMTP and SMPP alongside REST, where Vonage is REST-only.

Pricing and coverage. Vonage is pay-as-you-go per message/minute with volume discounts (approx. $0.0072 per US SMS segment); Sinch is pay-as-you-go per message with volume and committed-use pricing (approx. $0.0075 per US SMS segment). Vonage lists ~200 countries covered versus Sinch’s ~150. Both offer free developer credit, though Vonage publishes a specific amount (€2) while Sinch’s is unspecified.

How the request format differs

Source — Vonage:

curl -X POST 'https://rest.nexmo.com/sms/json' \
  -d 'api_key=YOUR_API_KEY' \
  -d 'api_secret=YOUR_API_SECRET' \
  -d 'from=Vonage' \
  -d 'to=15551234567' \
  -d 'text=Hello from Vonage'

Target — Sinch:

curl -X POST 'https://us.sms.api.sinch.com/xms/v1/YOUR_SERVICE_PLAN_ID/batches' \
  -H 'Authorization: Bearer YOUR_API_TOKEN' \
  -H 'Content-Type: application/json' \
  -d '{"from":"+15005550006","to":["+15551234567"],"body":"Hello from Sinch"}'

Endpoint / base URL. Vonage posts to rest.nexmo.com/sms/json (its legacy SMS API; the Messages API lives at api.nexmo.com/v1/messages). Sinch posts to a region-scoped host, us.sms.api.sinch.com, with your service plan ID baked into the path (/xms/v1/{service_plan_id}/batches).

Authentication. Vonage sends an API Key + API Secret as form fields in the request body (the Messages API uses JWT instead). Sinch uses a Bearer token in the Authorization header, so credentials move out of the payload and into a header.

Payload mapping. Vonage sends form-encoded fields; Sinch sends a JSON body. The fields map as: from → from (Sinch expects an E.164 number rather than an alphanumeric sender like “Vonage”), to → to but as a JSON array of numbers instead of a single string, and text → body.

Migration checklist

1. Create a Sinch account and generate an API token plus a service plan ID (self-onboarding is supported; free trial credit is available).
2. Map your request fields: from→from, to→to (wrap in an array, E.164), text→body, and switch from form-encoded to JSON.
3. Re-point your sending code to the region-scoped /batches endpoint and move auth from body params to an Authorization: Bearer header.
4. Re-test in Sinch’s sandbox before sending live traffic (Sinch provides one).
5. Update webhooks and delivery callbacks to Sinch’s delivery-report format and endpoints.
6. Run both providers in parallel, comparing delivery rates and cost.
7. Cut over once parity holds, then add new channels (Telegram, Apple Messages for Business, Email) if you want them.

For a from-scratch walkthrough of the target, see how to start with Sinch, and check the Sinch vs Vonage comparison for a full side-by-side.

Watch out for

• Free credit is unspecified. Sinch offers developer credit, but no amount is published, versus Vonage’s explicit €2.
• Narrower country coverage — ~150 countries versus Vonage’s ~200. Confirm your destination markets.
• Slightly higher list SMS price — ~$0.0075 versus ~$0.0072 per US segment, though committed-use pricing may offset this at volume.
• No Ruby or Kotlin SDK. If you rely on either, you will fall back to raw REST.
• Region-locked base URL. The us. host is region-specific; pick the region that matches your data-residency needs when you provision.