Customer.io

Customer.io lets you trigger messages based on what users actually do in your app—sign up, abandon cart, hit a milestone—not just time-based schedules.

What it does

It connects to your product data (via API or SDK) and lets you build workflows that send emails, push notifications, or SMS when specific events happen. You can segment users by attributes, actions, or custom properties, and A/B test message content and timing.

Best for

• Product teams who want behavioral email campaigns without a developer
• Growth marketers running lifecycle campaigns (onboarding, re-engagement, upsell)
• Companies with complex user journeys that need conditional logic

Strengths

• Real-time event processing—messages fire within seconds of user action
• Visual workflow builder with branching logic, not just linear sequences
• Supports email, push, SMS, and webhooks in one platform

• Behavioral triggers — Send messages based on any user action or attribute change
• Visual workflow builder — Drag-and-drop conditional paths without coding
• Segmentation engine — Filter users by events, properties, or custom SQL
• A/B testing — Test subject lines, content, timing, and sender names
• Multi-channel — Email, push notifications, SMS, and webhooks from one interface
• Real-time analytics — See open rates, click rates, and conversion per workflow