How to migrate from GatewayAPI to Vonage

GatewayAPI is a Danish SMS gateway and messaging platform (by ONLINECITY.IO) offering SMS, RCS and email APIs with pay-as-you-go pricing and EU data hosting. Vonage is a communications-API provider (part of Ericsson) covering SMS, voice, video and multi-channel messaging. On the messaging.dev Score, GatewayAPI rates 54/100 and Vonage 89/100 — the gap reflects broader channel coverage, more certifications and richer tooling on the Vonage side, which this guide walks through concretely.

What changes when you move

Channels you gain: MMS, WhatsApp, Viber, Facebook Messenger and Voice all become available on Vonage. Channels you keep: SMS and RCS are supported on both. The one channel you lose: GatewayAPI offers an Email API; Vonage does not, so any email sending has to move to a separate provider. Neither platform offers Telegram or Apple Messages for Business.

Compliance: both are GDPR-aligned. Vonage additionally holds ISO 27001, SOC 2 and HIPAA, none of which GatewayAPI lists — so you lose no certification by moving.

Data residency: both offer EU hosting and a data-residency choice. GatewayAPI is EU-only (no US servers); Vonage adds US servers plus APAC and Australia regions.

Pricing: both are pay-as-you-go with volume discounts. GatewayAPI runs on prepaid credit with no monthly fees, from €0.0061 per SMS. Vonage quotes from about $0.0072 per US SMS segment plus carrier fees, so re-model costs against your own destinations.

Tooling: GatewayAPI lists no official SDKs and no sandbox, with docs rated medium. Vonage ships SDKs for Node.js, Python, PHP, Java, C#, Ruby and Kotlin, offers a sandbox, and has docs rated high. Free credit exists on both sides — GatewayAPI grants test credits on request, Vonage a €2 trial credit. Note that GatewayAPI also exposes SMPP and Email-to-SMS interfaces; Vonage is REST-only.

How the request format differs

GatewayAPI — JSON body, token header:

curl https://gatewayapi.com/rest/mtsms \
  -H "Authorization: Token YOUR_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"sender": "ExampleSMS", "message": "Hello World", "recipients": [{"msisdn": 4512345678}]}'

Vonage — form-encoded body, key/secret:

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'

The endpoint changes from https://gatewayapi.com/rest/mtsms to https://rest.nexmo.com/sms/json (the legacy SMS API) or https://api.nexmo.com/v1/messages (the newer Messages API). Authentication moves from an Authorization: Token header to api_key + api_secret sent as request parameters on the SMS API, or JWT auth on the Messages API. Payload mapping: GatewayAPI’s sender becomes Vonage’s from; the message field becomes text; and GatewayAPI’s recipients array of { "msisdn": ... } objects collapses to a single to string. You also switch from a JSON request body to form-encoded parameters.

Migration checklist

1. Create a Vonage account and generate an API key and secret (or a JWT/application for the Messages API).
2. Map each request field: sender → from, message → text, recipients[].msisdn → to, and swap JSON for form-encoded parameters.
3. Re-point your sending code to the new base URL and replace the Authorization: Token header with key/secret (or JWT).
4. Re-test against Vonage’s sandbox before sending live traffic.
5. Update delivery-receipt/webhook callbacks to Vonage’s format and endpoints.
6. Run both providers in parallel and compare delivery on your real destinations.
7. Cut over once metrics match, then decommission the GatewayAPI path.

For a from-scratch setup, see How to start with Vonage; for a full field-by-field breakdown, see the GatewayAPI vs Vonage comparison.

Watch out for

• No Email channel. GatewayAPI’s Email API has no Vonage equivalent — email sending needs another provider.
• REST-only. Vonage drops the SMPP and Email-to-SMS interfaces GatewayAPI supports; any SMPP integration has to be rebuilt on REST.
• Two APIs, two auth models. Decide up front between the legacy SMS API (key + secret) and the Messages API (JWT) — they differ in payload and authentication.
• Pricing is quoted in USD per US segment plus carrier fees. Rebuild your cost model for your own routes rather than assuming parity with GatewayAPI’s EUR rates.