Asterisk vs Twilio Studio

Asterisk is a free, open-source framework for building communications applications and turning an ordinary computer into a communications server. It powers IP PBX systems, VoIP gateways, conference servers, call centers, voicemail servers, and IVR systems. Listed functions include call routing, recording, queuing, conferencing, voicemail, automated attendants, and call transfers. Computer-telephony interfaces include AGI, AMI, and the Asterisk REST Interface (ARI); listed VoIP protocols include SIP, H.323, IAX, Jingle/XMPP, MGCP, and SCCP. Asterisk can connect communications to applications, including CRM systems through AMI. The source code can be downloaded, and the project points users to installation on a modern cloud Linux instance. Building applications requires working knowledge of Linux, scripting, networking, and telephony. Asterisk is distributed under GPLv2; Sangoma offers commercial licensing for uses incompatible with that license. The Asterisk forum provides community help with installation, upgrades, and operation.

Twilio Studio is a visual builder for creating, editing, and managing communication workflows with low-code or no-code tools and optional custom code. Users place widgets on a canvas, and flows can start from inbound messages, voice calls, webhooks, or other Studio Flows. Workflows can handle voice, messaging, and other communication applications, and Studio can exchange data with backend systems to add context to Twilio-powered conversations. Twilio lists IVRs, appointment reminders, SMS surveys, call center workflows, autoresponders, and call forwarding as use cases. Its documentation includes tutorials for Slack, WhatsApp customer support menus, Twilio Conversations, and RCS messaging. The free tier includes 1,000 flow executions per month. A Flow can contain up to 2,000 widgets, including Subflows; an Execution ends after 1,000 steps or 30 days, and Execution and Step data is retained for 30 days after an Execution starts. Outbound HTTP requests from specified widgets are limited to 10 seconds. Additional Twilio communications charges are separate.