Documentation / VoiceML

Everything you need to ship and migrate VoiceML workloads.

VoiceML is VoiceTel's XML-based programmable voice runtime — Twilio-compatible verbs, signed webhooks, recordings, conferences, queues, and a REST surface centered on voice. This hub groups the overview, guides, reference material, and tooling that build on the runtime.

VoiceML overview Migrate from Twilio

Overview and migration

  • VoiceML overview

    What VoiceML is, the compatible surface, what's different, and the FAQ for engineers evaluating a Twilio-compatible voice runtime.

  • Migrate from Twilio

    Four-step migration with SDK host-override examples in Node, Python, Go, C#, PHP, Java, and Ruby plus webhook-signature verification.

Guides

  • Call recording and SIPREC

    Capture WAV files to your own Amazon S3 bucket via <Record> / <Dial> / <Conference>, or fork live media to your SIPREC-compatible Session Recording Server.

  • Speech recognition with <Gather>

    Transcribe caller speech with your own Deepgram, AWS Transcribe, Azure Speech, Google, OpenAI, or whisper.cpp account. Same provider powers <Connect><ConversationRelay>.

  • Text-to-speech with <Say>

    Built-in voices in four languages, plus bring your own Polly, Azure, ElevenLabs, Deepgram Aura, or Cartesia Sonic for studio-quality speech.

Reference

  • Compatibility matrix

    Every verb, attribute, REST resource, and caveat labelled supported, partial, roadmap, or out of scope — line by line against the spec.

  • VoiceML API reference

    Redoc-rendered OpenAPI for the Twilio-compatible REST surface — Calls, Conferences, Queues, Applications, Recordings, IncomingPhoneNumbers, the full SIP-trunking family, and more.

  • Voice-markup validator

    Paste a document into the in-browser validator to check verb shape and attribute compatibility before pointing live traffic at it.

Tools and SDKs

  • Migration calculator

    Model a real monthly workload against Twilio list pricing — minutes, recordings, and per-call costs side by side with VoiceTel rates.

  • VoiceML SDKs

    Official client libraries for the VoiceML REST surface in Python, TypeScript, Go, Java, C#, PHP, Ruby, and Swift.