SignalWire

Build and scale voice, messaging, video, fax, and AI experiences on shared programmable communications infrastructure.

Move existing Twilio applications to SignalWire with minimal code changes while retaining compatible call and messaging workflows.

Build customizable voice, messaging, and AI workflows using readable YAML or JSON, hosted on SignalWire or your own server.

Create and manage voice applications visually without code, while retaining options for SWML and external API integrations.

Build browser-based voice, video, and chat experiences with custom interfaces or prebuilt calling components.

Control live calls and respond to communications events from application code using real-time WebSocket connections and SDKs.

Give users, agents, and devices addressable identities with presence and multi-device reach.

Connect existing telephony to programmable call flows while retaining current infrastructure and carrier relationships.

Place communications infrastructure in a dedicated region to support compliance, data sovereignty, latency, and availability needs.

Run an enterprise FreeSWITCH deployment on your infrastructure with commercial modules, expert support, patches, and an SLA.

Get expert engineering help to scope, architect, and migrate SignalWire deployments.

Choose support coverage with defined response commitments and dedicated assistance for mission-critical applications.

SignalWire Programmable Unified Communications Platform

SignalWire brings voice, messaging, video, fax, and AI together under one control plane. The platform manages interaction state, lifecycle, and routing, while applications define behavior through code, APIs, declarative call flows, or SDKs. It supports real-time communications over PSTN, SIP, and WebRTC, along with messaging, video conferencing, fax, and AI and human-agent workflows. Developers can build and operate communications applications using SWML, REST APIs, and real-time SDKs. Voice capabilities include calling, IVR, routing, recording, transcription, conferencing, and audio streaming. Messaging supports SMS, MMS, RCS, and WhatsApp, with WhatsApp described as beta. Video supports programmable rooms, recording, and RTMP streaming. Fax supports programmatic sending and receiving.

Category: Communications Platform as a Service

• Build On Native Carrier-Grade Infrastructure
  Use voice and media capabilities on infrastructure operated by SignalWire, with native PSTN, SIP, and WebRTC connectivity.
• Keep Interaction State In One Place
  Rely on the platform to retain interaction state and context throughout a call, including when it is transferred.
• Program Call Flows And Routing
  Define call handling, routing decisions, IVR behavior, queues, and transfers in application code or declarative flows.
• Govern Agent Actions With Code
  Set the steps an agent follows and the tools and data available at each step, while keeping authoritative decisions in application code.
• Run AI Inside The Media Engine
  Use AI capabilities integrated with the communications media path rather than connecting calls to separate AI and orchestration services.
• Unify Communications On One Platform
  Build voice, video, messaging, fax, and AI experiences through a common programmable platform.
• Send And Receive Faxes Programmatically
  Integrate inbound and outbound fax workflows into applications through the API and compatible cXML controls.
• Create And Join Programmable Video Rooms
  Create rooms through APIs and connect browser participants for conferencing, screen sharing, and room-layout control.
• Transfer Calls Without Losing Context
  Move an interaction between agents or to a human while preserving its history and context.
• Build Flows With APIs And SDKs
  Use declarative call flows, REST APIs, or real-time SDKs to build and control communications behavior in application code.
• Connect Agents To Your Systems
  Let agents retrieve current information and trigger application-defined actions while controlling which tools and data are available.
• Serve Voice And Text Conversations
  Reuse agent behavior and tools across supported voice and text channels instead of maintaining separate agent definitions.
• Reach Customers Across Messaging Channels
  Send and receive messages across supported channels and use delivery and reply events in application workflows.
• Reuse Twilio-Style Integration Code
  Move compatible applications to SignalWire by updating endpoints and credentials, with minimal code changes in many cases.
• Address And Connect Communications Resources
  Reach subscribers and communications resources directly by address, then connect them through programmable workflows.
• Scale Communications On Carrier-Grade Infrastructure
  Run communications workloads on infrastructure designed for carrier-scale traffic, with published service availability commitments.
• Process Speech And Generate Responses
  Support spoken conversations with integrated speech recognition, model orchestration, and speech synthesis.
• Inspect Agent Activity And Outcomes
  Review live events and conversation reports to understand agent behavior, tool activity, and outcomes.
• Provision Numbers And Register Campaigns
  Set up messaging numbers and complete the applicable campaign registration or verification process.
• Restrict Guest Access To Rooms
  Provide browser participants with credentials limited to the intended room while keeping the project API token on the server.
• Record And Stream Video Rooms
  Record video sessions and stream video rooms to an RTMP destination using available controls.
• Track Communications In One Event Stream
  Review communications events and outcomes across platform channels in a unified operational view.
• Ground Agents In Your Data
  Connect agents to knowledge sources so they can retrieve information during conversations.
• Record And Transcribe Calls
  Capture calls and obtain transcriptions using the available recording and transcription capabilities.
• Support High-Throughput Communications
  Use carrier-grade infrastructure and available capacity options for communications workloads, subject to applicable limits.
• Add Conferencing And Audio Streaming
  Build conferencing and call-audio streaming or tapping into programmable voice applications.
• Track Call Outcomes
  Use call event notifications to monitor call results and trigger application actions.

Compatibility API

SignalWire’s Compatibility API provides a migration path for applications built with Twilio’s TwiML, REST API, or helper libraries. It supports TwiML-compatible cXML instructions, REST endpoints, and client SDKs. Migration typically involves replacing credentials, changing the API endpoint when needed, and pointing phone number webhooks to SignalWire; existing TwiML/cXML response handlers work without modification. Supported capabilities include voice, messaging, fax, phone number management, and voice and messaging application configurations. AI is not supported in the Compatibility API.

Category: Communications Platform as a Service

• Migrate With Minimal Code Changes
  Keep much of an existing integration in place while moving it to SignalWire by replacing credentials, changing endpoints where applicable, and updating webhook URLs.
• Reuse Existing REST Request Patterns
  Use familiar Twilio-style REST requests with SignalWire by changing credentials and, where applicable, the API base URL.
• Reuse TwiML-Compatible Call Instructions
  Retain compatible XML instructions for call, message, and fax control, including existing TwiML/cXML response handlers.
• Build With Familiar Client Libraries
  Use compatibility helper libraries to generate cXML and make REST API calls in supported languages.
• Manage Calls And Call Workflows
  Use supported voice features for inbound and outbound calls, call control, conferencing, queues, recordings, and transcriptions.
• Send Messages And Faxes
  Use compatible API features to send and receive SMS, MMS, and faxes, with status callbacks for messaging.
• Purchase And Manage Phone Numbers
  Use compatible API features to purchase phone numbers and manage their configuration.
• Manage Voice And Messaging Applications
  Configure and manage application settings for voice and messaging using supported API features.

SignalWire Markup Language (SWML)

SWML is a declarative markup and scripting language for building communication applications in YAML or JSON. Its Calling and Messaging document types define instructions for voice-call flows, inbound SMS and MMS handling, routing, replies, and AI agent behavior. Scripts can be hosted by SignalWire, served from your own server, or generated with a Server SDK. SWML supports reusable sections, control flow, dynamic variable substitution, native AI and function integrations, and external API requests.

Category: Communications Platform as a Service

• Define Flows In YAML Or JSON
  Describe what SignalWire should do in a readable document rather than expressing the workflow as low-level application logic.
• Build Voice And Messaging Workflows
  Define call handling and inbound text-message behavior within the same markup language.
• Control Calls And Routing
  Specify call actions and organize routing logic in a single script, including branching and reusable sub-flows.
• Configure AI Agents And Tools
  Define agent behavior and tool access alongside call-flow instructions, and connect agents to application functions.
• Use Dynamic Data In Flows
  Reference call, message, and prior-step data in document values to tailor workflow behavior and responses.
• Deploy Scripts Your Way
  Choose hosted scripts, externally served instructions, or SDK-generated SWML to fit application development and operations.
• Reach External APIs From Flows
  Include API requests in communication workflows and define supported request and response handling in the SWML document.
• Catch Script Errors Before Deployment
  Use editor assistance and schema validation while writing scripts to spot type mismatches before deployment.

Call Flow Builder

Call Flow Builder is a no-code visual tool in the SignalWire Dashboard for creating and managing voice applications. Its drag-and-drop canvas arranges call-flow nodes into branches and decision points, with configurable options such as audio files or text-to-speech prompts. Flows can integrate external APIs or use SWML; the Builder generates valid SWML and includes versioning to support testing different configurations.

Category: Communications Platform as a Service

• Build Voice Applications Without Code
  Design call-handling logic in a visual tool rather than writing application code.
• Arrange And Connect Flow Nodes Visually
  Build and adjust a call flow on a canvas by positioning nodes and connecting them.
• Create Branches And Decision Points
  Shape call handling into paths with multiple branches and decision points.
• Extend Flows With APIs And SWML
  Connect call-flow logic with external APIs or use generated SWML for additional control.
• Configure Audio And Caller Prompts
  Set options for individual nodes, including audio files and text-to-speech prompts.
• Version And Test Flow Configurations
  Keep versions of call-flow configurations to support testing different setups.

Browser SDK

SignalWire’s JavaScript SDK lets developers add voice calling, video calling, and chat to web applications. It supports custom WebRTC experiences or prebuilt calling components. Developers can manage calls and participants, camera and microphone access, and screen sharing.

Category: Communications Platform as a Service

• Add Browser-Based Voice And Video Calling
  Build voice and video calling experiences directly into a website or web application using WebRTC.
• Add Real-Time Chat
  Give users a real-time chat experience within a website or application.
• Build Or Embed Calling Interfaces
  Design a custom calling experience or use prebuilt components to add calling functionality.
• Manage Calls And Device Controls
  Control calls, participants, camera and microphone access, and screen sharing in browser-based experiences.

RELAY SDKs

SignalWire RELAY SDKs let developers control calls programmatically through a persistent, event-driven WebSocket connection. The Relay client supports inbound and outbound calls and methods for answering, playing audio or text-to-speech, collecting caller input, recording, connecting or bridging calls, conferencing, and holding calls. It can also send and receive SMS and MMS, and start an AI agent session on a Relay-controlled call. SDKs are available in multiple programming languages, with the Relay client documented for Python and TypeScript.

Category: Communications Platform as a Service

• Control Calls As They Happen
  Use a persistent WebSocket connection to receive events and direct live calls from application code.
• Handle Inbound And Outbound Calls
  Build call handling into applications, from answering incoming calls to initiating outbound calls.
• Direct Call Actions From Code
  Build interactive call flows using SDK methods to play prompts, collect input, detect machines, and connect callers.
• Send Messages And Handle Replies
  Integrate SMS and MMS with call workflows by sending messages, receiving replies, and handling delivery results.
• Reconnect Automatically After Disconnects
  Let the client re-establish its WebSocket connection after disconnection with increasing retry delays.
• Build With Your Preferred Language
  Choose from SDKs in multiple languages to integrate SignalWire capabilities into a backend application.
• Manage Recording And Playback
  Control recordings and audio playback during calls, including pausing, resuming, and stopping these actions.
• Connect Calls And Join Conferences
  Route calls to other numbers, disconnect connections, or manage conference participation using call-control methods.
• Choose Which Calls Reach Your Client
  Subscribe to the call contexts your application handles, either at connection time or dynamically.
• Add An AI Session To A Call
  Start an AI agent session on a Relay-controlled call and provide its prompt and language configuration.

Subscribers

Subscribers are SignalWire platform resources that represent users and provide a foundation for user management. Each subscriber has a durable, addressable identity with its own addresses, presence, and multi-device reach. Applications can model users, agents, and devices as subscribers, with extensions, credentials, and routing rules, and address them directly.

• Address Users By A Stable ID
  Give each subscriber a durable identity that applications can address directly.
• Reach Users Across Their Devices
  Use a subscriber's presence and multiple addresses to represent how that identity can be reached across devices.
• Manage Extensions And Routing Rules
  Associate extensions, credentials, and routing rules with each subscriber identity.
• Authorize Subscriber-Scoped API Requests
  Use a Subscriber Access Token to authenticate API requests that operate on an individual subscriber.

Programmable SIP

Programmable SIP provides full SIP-stack control for existing telephony without requiring a rip-and-replace. Connect existing PBX, SBC, or carrier infrastructure through SignalWire and adopt the platform incrementally while retaining current carrier relationships. SIP endpoints can be addressed and connected through declarative call flows, including sequential dialing with timeouts and fallback.

Category: Communications Platform as a Service

• Connect Existing Telephony
  Bring existing PBX, SBC, and carrier infrastructure into SignalWire without a full rip-and-replace.
• Control The SIP Stack
  Program and manage SIP within the platform.
• Route Calls Across SIP Endpoints
  Build call flows that reach SIP endpoints in sequence or route to other destinations with configurable timeouts and fallback behavior.
• Program SIP Call Behavior
  Set call handling and routing behavior, including ring time and fallback order, and receive call outcome events.
• Set SIP-Level Metadata
  Add custom headers to outbound calls to provide SIP-level metadata for routing, tracing, and integration.

Dedicated Real-Time Regions

Dedicated Real-Time Regions provide single-tenant infrastructure that can be pinned to a region for compliance, latency, and data-sovereignty requirements. The regions include a 99.99% availability guarantee for mission-critical workloads.

Category: Communications Platform as a Service

• Place Infrastructure In A Region
  Choose a region for infrastructure placement to meet regional compliance, latency, and data-sovereignty needs.
• Use Dedicated Single-Tenant Infrastructure
  Run on dedicated, single-tenant infrastructure rather than shared infrastructure.
• Support Mission-Critical Availability
  Receive a 99.99% availability guarantee for mission-critical workloads deployed in Dedicated Real-Time Regions.

FreeSWITCH Advantage

FreeSWITCH Advantage is SignalWire’s paid, self-hosted enterprise branch of FreeSWITCH. It includes commercial modules such as G.729A and answering machine detection, founder-level support, patches, and an SLA. Customers run the software on their own infrastructure.

• Get Founder-Level Support
  Receive founder-level commercial support for enterprise FreeSWITCH deployments.
• Access Commercial Telephony Modules
  Use commercial modules such as G.729A and answering machine detection within a self-hosted FreeSWITCH deployment.
• Receive Patches And SLA Coverage
  Receive patches and service-level agreement coverage for the enterprise offering.
• Run FreeSWITCH On Your Infrastructure
  Operate the FreeSWITCH deployment on your own infrastructure with the commercial modules and support associated with the Advantage edition.

Professional Services

SignalWire Professional Services support enterprise deployments with engineers who scope and architect alongside customer teams. The service provides direct platform expertise and is available for assisted migrations.

• Plan And Architect Your Deployment
  Work directly with SignalWire engineers to scope and architect a deployment alongside your team.
• Work With Platform Experts
  Engage engineers with direct SignalWire platform expertise for enterprise deployment work.
• Get Help Migrating To SignalWire
  Use Professional Services for assisted migration when moving communications workloads to SignalWire.

SignalWire Support Plans

SignalWire Support Plans offer Basic, Premium, and Enterprise coverage for customers at different stages of growth. Basic is free and includes email and community support. Premium costs 5% of monthly usage or a minimum of $1,200 per month and includes priority-based response SLAs and a customer success representative. Enterprise costs 8% of monthly usage or a minimum of $5,000 per month, with faster SLAs, 24/7 expert access, a named technical manager, a dedicated escalation hotline and Slack channel, and quarterly account reviews.

• Choose Coverage That Fits Your Needs
  Select from free Basic support, Premium support with SLAs and a customer success representative, or Enterprise support with dedicated services.
• Set Clear Response-Time Expectations
  Defined targets by issue priority clarify when to expect a response, with Enterprise providing the shortest listed response targets.
• Reach Experts Around The Clock
  Access expert assistance 24/7 through paid support plans, including coverage for mission-critical applications.
• Work With A Named Technical Manager
  Enterprise customers receive a named technical manager as part of their support coverage.
• Escalate Issues Through Dedicated Channels
  Use the Enterprise plan’s dedicated hotline and Slack channel to contact support.
• Review Your Account Quarterly
  Enterprise customers receive a quarterly account review as part of their support plan.