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Advanced communications from the source. | SignalWire

SWML: The Best Way to Build and Maintain Your Call Flows

What is SWML?

Advanced Technical Success Manager

André Martins

In the rapidly evolving world of real-time communications, managing call flows and customizing communication channels can be complex and overwhelming. SignalWire Markup Language (SWML) is here to change that. In this post, we'll explore how SWML is reshaping call flows and developer experiences.

Empowering Seamless Communication

SWML is a revolutionary JSON and YAML-based document markup language that empowers you to define call flows and customize Interactive Voice Response (IVR) systems. What sets SWML apart is its unparalleled flexibility and power to blur lines of communication across multiple kinds of resources. This is all thanks to its integration with FreeSWITCH.

Key Features of SWML

SWML boasts several key features that propel it beyond traditional CPaaS solutions:

Native Support in Call Flow Builder
SignalWire's Call Flow Builder is a no-code application builder that provides an intuitive visual interface, making the creation of intricate call flows a breeze. By leveraging a user-friendly drag-and-drop approach, you can effortlessly add IVR functions, define AI behaviors, and create seamless communication experiences, all without writing a single line of code.

SWML’s Unique Structure
If you prefer to write SWML directly instead using a visual builder, that’s no problem! SWML’s descriptive format is made up of Sections, Statements, and Methods.

Sections are ways to compartmentalize Statements and Methods. Statements allow you to manage the flow of calls and their state, and Methods allow you to perform actions on calls.

Have a look at our SWML Technical Reference to learn more about all the supported statements and methods!

The AI Method
Through SWML’s AI method, you can unleash the potential of AI-powered IVRs to build virtual assistants capable of human-like conversation and engaging with callers in multiple languages.

From gathering information to executing remote procedures through SignalWire's AI Gateway, the possibilities for enhancing customer experiences and process automation are endless.

How simple is it to create an AI Agent using SWML? Here is an example in YAML of defining an AI assistant that answers calls for you to take messages and pass them on to a given URL:

In this example, you can hear what the AI agent actually sounds like.

Say goodbye to complicated phone trees that lead to human agents wasting time with trivial tasks! SignalWire’s AI Agent understands the caller’s intent within the first few seconds of the call, immediately routing calls appropriately or recording relevant information.

SWML vs Traditional CPaaS Solutions

SWML includes a few features that put it ahead of traditional CPaaS solutions:

Unlike older XML-based solutions, SWML's JSON and YAML format aligns with modern industry standards. While you can use SWML without a server, you can also use native functionality of your preferred language to write SWML in JSON format, and return it using a web server for SignalWire to run on a given call.

Easy-to-maintain call flows
SWML allows you to express entire call flows within a single document, streamlining management between sections. The result? Lower complexity and higher performance, opening doors for low-code and no-code possibilities.

With older solutions, you’d have to jump from webhook to webhook, with the end result being multiple jumps all in different places, and no clear way to see where things happen on a given call. With SWML, your call flow exists in a single document, and it’s much easier to jump from section to section:

This leads to much less time going back and forth in your code to find where your call flow goes under different conditions, and it also improves performance due to not needing to generate new requests to fetch more instructions.


With SWML, call flows and communication experiences are transformed forever. Whether you’re building AI-powered IVRs, optimizing call queues, or hosting multi party conferences, SWML unlocks the potential for personalized, efficient, and secure communication, all while respecting development workflows.

So, don't drown in a sea of webhooks—leverage the power of SignalWire Markup Language and take your communication systems to new heights. Discover the transformative capabilities of SWML by signing up for a SignalWire Space today, and re-shape the future of real-time communications!

To learn more about SignalWire's capabilities, visit, and join the vibrant SignalWire community on Slack or our Forum to interact with the team and share your projects. We can't wait to see what you build!

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