Compatibility

Know exactly which call features are supported before migration.

Every verb, attribute, REST resource, and caveat is published with a clear support status — supported, partial, roadmap, or unsupported — so you can see exactly what migrates cleanly before you cut traffic over.

View matrix Validate VoiceML Migration guide

Voice markup compatibility matrix

Legend: ✓ Supported ◐ Partial ✗ Unsupported N/A Out of scope

Resource	Endpoints	VoiceTel	Notes
Calls	`POST /Calls`	✓	Normalises To/From against per-tenant phone regions; `MachineDetection` truly optional (matches Twilio — omit it and no AMD runs); `Twiml`/`ApplicationSid` accepted; per-call SIP/auth params (`SendDigits`, `SipAuthUsername`/`SipAuthPassword`, `Timeout`, `CallReason`) wired through to the originate.
	`GET /Calls/{Sid}`	✓
	`GET /Calls` (filters: To, From, Status, ParentCallSid, StartTime≥/≤, EndTime≥/≤, Page, PageSize≤1000)	✓	Full Twilio query surface; `EndTime` auto-restricts to terminal-status rows.
	`POST /Calls/{Sid}` (Status / Twiml / Url / FallbackUrl / StatusCallback*)	✓	Full Call resource on success; `Twiml` wins over `Url`; `StatusCallback*` swaps the live lifecycle-webhook wiring.
	`DELETE /Calls/{Sid}`	✓
Calls / Recordings	`GET /Calls/{Sid}/Recordings`	✓
	`GET /Calls/{Sid}/Recordings/{Sid}`	✓
	`POST /Calls/{Sid}/Recordings` (start mid-call)	✓	Honours `RecordingMaxDuration` / `PlayBeep` / `RecordingStatusCallback*`.
	`POST /Calls/{Sid}/Recordings/{Sid}` (Status=stopped/paused/in-progress)	✓	Stop, pause, resume; idempotent against already-completed.
	`DELETE /Calls/{Sid}/Recordings/{Sid}`	✓	Unlinks WAV and drops row.
Calls / Streams	`GET /Calls/{Sid}/Streams[/{Sid}]`	✓	Live tracker; list returns 0 or 1 (one fork per call).
	`POST /Calls/{Sid}/Streams` (start)	✓	Mirrors `<Connect><Stream>` / `<Start><Stream>`; returns MZ-prefixed SID.
	`POST /Calls/{Sid}/Streams/{Sid}` (Status=stopped)	✓
Calls / Siprec	`GET /Calls/{Sid}/Siprec[/{Sid}]`	✓	Live tracker.
	`POST /Calls/{Sid}/Siprec` (start)	✓	Mirrors `<Start><Siprec>`; returns SR-prefixed SID.
	`POST /Calls/{Sid}/Siprec/{Sid}` (Status=stopped)	◐	Clears tracking; underlying SIPREC module has no stop verb (recording continues until call hangup).
Calls / Transcriptions	`GET /Calls/{Sid}/Transcriptions[/{Sid}]`	✓	Live tracker.
	`POST /Calls/{Sid}/Transcriptions` (start)	✓	Mirrors `<Start><Transcription>`; returns RT-prefixed SID.
	`POST /Calls/{Sid}/Transcriptions/{Sid}` (Status=stopped)	✓
Calls / Payments	`POST /Calls/{Sid}/Payments[/{Sid}]`	✗	`<Pay>` not implemented (PCI-DSS scope); path returns 404 — half-implementing PCI is more dangerous than a clean 404.
Calls / Events	`GET /Calls/{Sid}/Events`	◐	Compatibility stub: 200 + empty list. Equivalent data delivered via the customer's `StatusCallback` URL — empty-list shape keeps SDK iterators clean.
Calls / Notifications	`GET /Calls/{Sid}/Notifications`	◐	Compatibility stub: 200 + empty list. Operator-side events flow through Prometheus and structured logs.
Calls / UserDefinedMessages	`POST /Calls/{Sid}/UserDefinedMessages`	✗	Returns 501 + Twilio error code 20501 (chat-style live-call messaging needs websocket message-passing infrastructure that's out of scope).
Conferences	`GET /Conferences`	✓	Live conference query, multi-tenant namespaced.
	`GET /Conferences/{Sid}`	✓
	`POST /Conferences/{Sid}` (`Status=completed` to end)	✓
Conferences / Participants	`GET /Conferences/{Sid}/Participants[/{Sid}]`	✓
	`POST /Conferences/{Sid}/Participants/{Sid}` (Muted, Hold)	✓	Mute/unmute and hold/unhold both wired.
	`DELETE /Conferences/{Sid}/Participants/{Sid}` (kick)	✓
Conferences / Recordings	`GET /Conferences/{Sid}/Recordings`	✓	Metadata persisted at conference start; pagination envelope same as `/Recordings`.
Queues	`POST /Queues`, `GET /Queues[/{Sid}]`, `POST /Queues/{Sid}`, `DELETE /Queues/{Sid}`	✓	Full CRUD; in-process state.
Queues / Members	`GET /Queues/{Sid}/Members[/{Sid}\|Front]`, `POST /Queues/{Sid}/Members/{Sid\|Front}`	✓	VoiceTel extension — REST dequeue alongside `<Dial><Queue>` markup.
Applications	`POST /Applications`, `GET /Applications[/{Sid}]`, `POST /Applications/{Sid}`, `DELETE /Applications/{Sid}`	✓	Voice-only fields (no SMS).
Recordings (top-level)	`GET /Recordings[/{Sid}]`	✓
	`DELETE /Recordings/{Sid}`	✓	Row + local WAV + S3 object (best-effort).
	`GET /Recordings/{Sid}.wav`	✓	Binary `audio/wav` with three-state delivery: 200 (local), 302 to presigned S3 URL (archived), 410 Gone (cleaned up). All HTTP clients follow the 302 transparently.
IncomingPhoneNumbers	`GET /IncomingPhoneNumbers`	✓	Tenant-scoped list of DIDs assigned to the authenticated account.
	`POST /IncomingPhoneNumbers`	✓	Self-serve DID assignment by E.164. Idempotent on the same tenant; 409 if the number is claimed by another account. Inventory itself is provisioned via the VoiceTel Numbers workflow.
	`GET /IncomingPhoneNumbers/{Sid}`	✓	Cross-tenant fetches 404 with the same shape as a nonexistent number — no enumeration leak.
	`POST /IncomingPhoneNumbers/{Sid}`	✓	Only-set-fields-touched update semantics for voice routing on an assigned DID.
	`DELETE /IncomingPhoneNumbers/{Sid}`	✓	Idempotent release: 204 on success or if the number was already gone.
AvailablePhoneNumbers	`GET /AvailablePhoneNumbers/{Country}/Local` etc.	✗
OutgoingCallerIds	full sub-resource	✗
ShortCodes	full sub-resource	✗
Sip / Domains CredentialLists IpAccessControlLists	full sub-resource	✗	SIP-domain provisioning handled by the SIP trunking workflow.
Messages MMS	`POST /Messages` etc.	N/A	Compatibility surface is voice-only. See VoiceTel Messaging for the native messaging product.
Pricing API	full	N/A	VoiceTel publishes rates directly; no Twilio-shaped pricing API.
Insights	full	N/A	Twilio-hosted analytics product.
Verify Lookup Studio TaskRouter Conversations Chat Video Proxy Functions/Assets Wireless Trunking Authy	full	N/A	Distinct Twilio products, out of scope for the compatibility surface.