How to migrate from SMSAPI to Sinch

SMSAPI is a Polish business-messaging platform (a brand of LINK Mobility Poland) offering bulk SMS, MMS, VMS voice, RCS and WhatsApp Business messaging over a REST API. Sinch is a larger cloud-communications platform covering messaging, voice and email APIs from a single account. On the messaging.dev Score, SMSAPI rates 44/100 and Sinch 92/100 — the sections below lay out what actually differs so you can plan the move as data, not marketing.

What changes when you move

Channels you gain, none you lose. Both providers cover SMS, MMS, RCS, WhatsApp and voice. Moving to Sinch adds Viber, Facebook Messenger, Telegram, Apple Messages for Business and email — five channels SMSAPI does not offer. No channel you rely on today disappears.

Compliance. SMSAPI is GDPR and ISO 27001 aligned. Sinch keeps both and adds SOC 2 and HIPAA, so you gain certifications rather than losing any.

Data residency. SMSAPI hosts within the EU only, with no region choice. Sinch offers both EU and US data residency, a residency choice, and additional regions (APAC, Australia, Brazil).

Pricing. SMSAPI uses prepaid pay-as-you-go credit (minimum top-up around €30, from ~€0.04 per SMS). Sinch is pay-as-you-go per message with volume and committed-use pricing (approx. $0.0075 per US SMS segment). Both include free developer credit and self-service onboarding.

Tooling that stays the same. Both ship high-quality docs and a sandbox test environment, and both expose REST and SMTP (Sinch adds SMPP). Official SDKs overlap on PHP, Python, Java and C#; SMSAPI’s JavaScript SDK maps to Sinch’s Node.js SDK, but SMSAPI’s Go and Bash SDKs have no official Sinch equivalent.

For a fuller side-by-side, see Sinch vs SMSAPI.

How the request format differs

SMSAPI quickstart:

curl -X POST -H "Authorization: Bearer YOUR_API_TOKEN" "https://api.smsapi.com/sms.do?to=48500000000&from=SenderName&message=Hello+world&format=json"

Sinch quickstart:

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"}'

Three things change:

• Endpoint. You swap https://api.smsapi.com/sms.do for https://us.sms.api.sinch.com/xms/v1/{service_plan_id}/batches. Sinch embeds a service_plan_id in the URL path; SMSAPI has no equivalent.
• Auth. Both use a Bearer token in the Authorization header, so the header itself is unchanged — only the token value differs. SMSAPI describes it as an OAuth 2.0 API token; Sinch as an API token.
• Payload. SMSAPI passes fields as URL query parameters: to (a single number), from (the sender name) and message (the URL-encoded body). Sinch sends a JSON body instead: to becomes an array of numbers, from is the sender, and the message text moves to body. You also add a Content-Type: application/json header.

Migration checklist

1. Create a Sinch account, then copy your API token and note the service_plan_id from the dashboard.
2. Map each SMSAPI field to Sinch: to → to[], from → from, message → body.
3. Re-point your sending code from sms.do query strings to a JSON POST against the Sinch batches endpoint.
4. Re-test in Sinch’s sandbox before sending any live traffic.
5. Update your delivery-report webhooks and callbacks to Sinch’s format.
6. Run both providers in parallel and compare delivery results.
7. Cut over once Sinch matches your baseline; the new-provider walkthrough is in how to start with Sinch.

Watch out for

• The default endpoint is the US region. The quickstart uses us.sms.api.sinch.com. Sinch supports EU residency, but you must select the EU cluster and endpoint explicitly if EU data residency matters to you.
• No official Go or Bash SDK. If your SMSAPI integration relies on the Go or Bash SDK, you will drop to raw REST or another supported language on Sinch.
• A new required service_plan_id. It is part of every request path — a concept SMSAPI does not have.
• Recipients become an array and the body moves into JSON. Any code that builds SMSAPI query strings needs rewriting to construct a JSON payload.