Migrating from Sinch to Twilio involves porting phone numbers from Sinch to Twilio, replacing Sinch REST API or SDK calls with Twilio equivalents, updating webhook formats, completing A2P 10DLC registration, and running a parallel validation period where both carriers serve traffic simultaneously so delivery quality can be confirmed before Sinch is decommissioned. Businesses migrate from Sinch to Twilio for access to Twilio's broader product portfolio including Twilio Flex, Studio, and Conversations, for more transparent pricing and usage dashboards, and to consolidate voice and SMS under a single vendor with global support coverage. The parallel-run migration approach is particularly recommended for Sinch migrations because delivery routes differ between carriers and some destination markets may perform differently under each provider, requiring empirical validation before full cutover.
What You Need Before You Start
Create a Twilio account and complete business identity verification, then navigate to the Twilio Console to create your first Messaging Service under Messaging, then Services, which will serve as the pooled sender resource for ported numbers and simplify routing management during the parallel-run period. Export your Sinch number inventory from the Sinch Customer Dashboard at dashboard.sinch.com by navigating to Numbers, then Your Numbers, selecting all numbers, and documenting each number's country, type, and the Service Plan ID it is currently assigned to, as Sinch assigns numbers to service plans rather than individual applications. Begin Twilio A2P 10DLC Brand registration immediately even before starting the port request, as the brand registration requires business information verification that takes 1 to 5 business days and is a prerequisite for US ported numbers to send SMS on Twilio. Audit your application code for Sinch SDK references including @sinch/sdk-core in Node.js, sinch-sdk in Python, or com.sinch in Java Maven imports, and for each Sinch API call document the equivalent Twilio call so you have a complete substitution map before writing any new code.
Step-by-Step Integration Guide
Submit port requests for Sinch numbers through the Twilio Console under Phone Numbers, then Port and Host, entering the numbers in E.164 format and uploading an LOA signed by the business account holder, with the account name matching your Sinch billing name, your Sinch account number from the Sinch Dashboard under Account Settings, and expecting 3 to 7 business days for US local number ports with Sinch as the losing carrier. Replace Sinch outbound SMS API calls by updating the Sinch sendSms call from await sinchClient.sms.batches.send({ from: fromNumber, to: [toNumber], body: body }) to the Twilio equivalent await twilioClient.messages.create({ from: fromNumber, to: toNumber, body: body }), noting that Sinch uses a batches.send endpoint that accepts an array of recipients while Twilio's create call is per-message and requires a loop for multiple recipients. Run both Sinch and Twilio in parallel for 7 days during the validation period by adding a percentage-based routing decision in your outbound SMS dispatch function: route 10% of outbound messages through Twilio for the first 2 days, increase to 50% for days 3 and 4, and increase to 100% for days 5 through 7, comparing delivery receipts from both carriers daily using the Twilio Console message logs and the Sinch Dashboard reporting. Update inbound webhook handling by replacing Sinch webhook field names servicePlanId, from, to, body, and id with Twilio's AccountSid, From, To, Body, and MessageSid, and add Twilio signature validation using twilio.validateRequest with your Twilio Auth Token to replace Sinch's webhook token validation header.
Common Issues and How to Fix Them
Sinch supports sending to multiple recipients in a single API batch call using the to array with up to 1,000 numbers, and application code written to leverage this batch sending must be rewritten for Twilio because Twilio's Messages API create endpoint accepts only a single recipient per call. Implement a batch dispatch wrapper function in your application that iterates over the recipient array, calls client.messages.create for each recipient using Promise.all for concurrent sends up to the Twilio API rate limit, and collects all resulting MessageSids into an array for tracking, replacing the single Sinch batch call semantics with parallel Twilio calls. Sinch routes international SMS through different carrier agreements than Twilio, and some destination countries may show lower delivery rates on Twilio during the parallel validation period due to carrier relationship differences, particularly for markets in Southeast Asia, Latin America, and parts of Africa. Compare per-country delivery rates during the parallel run rather than aggregate rates, and for any country showing more than 5% lower delivery on Twilio open a support ticket with Twilio to request alternative routing before completing the full cutover. The Sinch webhook for MMS or rich messaging deliveries includes attachments in a mediaList array field, while Twilio delivers MMS attachments as top-level fields NumMedia, MediaUrl0, MediaContentType0, and so on for each attachment index, causing MMS webhook handlers written for Sinch to miss attachment data after the cutover. Update MMS webhook handlers to read Twilio's indexed media fields by iterating from index 0 to parseInt(request.body.NumMedia) - 1 and accessing request.body['MediaUrl' + i] and request.body['MediaContentType' + i] for each attachment, replacing the Sinch mediaList array access pattern.
How to Get More from This Integration
Build a per-country delivery comparison dashboard during the parallel validation period by logging each outbound message dispatch with carrier, destination country, timestamp, and status to a database, querying the Twilio message status webhook for delivered, undelivered, and failed outcomes, and displaying a side-by-side delivery rate comparison by country in a simple admin dashboard so you can identify any destination markets where Twilio needs routing optimization before the full cutover. Add Twilio Verify as a replacement for Sinch Verification by creating a Twilio Verify Service in the Console under Verify, then Services, replacing your Sinch verification SDK calls with Twilio Verify API calls at POST https://verify.twilio.com/v2/Services/{ServiceSid}/Verifications and POST https://verify.twilio.com/v2/Services/{ServiceSid}/VerificationChecks, gaining Twilio's global verification routing optimization that dynamically selects the best delivery path per destination country. Implement Twilio Advanced Opt-Out Management after migrating Sinch numbers by ensuring your Messaging Service has opt-out keywords enabled and that STOP replies received during the Sinch parallel period are imported as opted-out contacts in Twilio by calling POST https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages.json with a To parameter set to the opted-out phone to generate a test request, then checking opt-out status via the Twilio Advanced Opt-Out API. Migrate Sinch voice calls to Twilio Programmable Voice by replacing Sinch SVAML (Sinch Voice Application Markup Language) responses with Twilio TwiML equivalents, converting Sinch's RunMenu action to Twilio's Gather verb, Sinch's PlayFiles action to Twilio's Play verb, and Sinch's ConnectPSTN action to Twilio's Dial verb with a Number noun, maintaining the same IVR call flow logic in a new TwiML-based implementation.
Conclusion
Migrating from Sinch to Twilio with a parallel validation period ensures that delivery quality is empirically verified for every destination market before production traffic is fully committed to Twilio. Contact Telphi Consulting to plan and execute your Sinch to Twilio migration including number porting, code migration, and parallel validation management.
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