Messaging for builders
Send transactional email, push, and in-app from your terminal, your agent, or your stack. Test mode is free. Add $10 in funds when you're ready to send to real users.
- No monthly commitment
- Top-ups for as little as $10
- Grows with you from alpha through IPO
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Ship messaging in minutes, not days
Sign up
Create an account in the browser or from the CLI—wherever you're most comfortable.
Send your first email
Point Customer.io at your sending domain and fire off a message to verified test users. Test mode is free—no credit card needed.
Unlock external sends
When you're ready to reach real subscribers, add $10 in funds. That's your only cost until you outgrow pay-as-you-go.
Work in the tools you like best
CLI
Script and automate messaging operations directly from the terminal. Sign up, configure your domain, and send—all without leaving your shell.
Web Interface
Manage workspaces, compose messages, and inspect activity from a familiar web UI. Drag-and-drop or code—your call.
MCP Server
Connect Customer.io to any MCP-compatible environment. Create profiles, trigger workflows, and send messages without opening the app.
Simple, usage-based pricing
Send emails to people on your team for free, plus 100 free messages each on push, in-app, and webhook. When you add at least $10 in funds you can send to anyone.
What you get | Test mode (free) | With funds |
|---|---|---|
Recipients | 10 verified test users | Anyone |
Cost per message | Free | $0.40 per 1,000 messages |
Every channel
Email, push, in-app, and webhook—one API, one SDK, one pricing tier.
Transactional and broadcast
Send transactional messages to individuals. Run one-off broadcasts to static lists and groups.
Rich profiles + history
Every send rolls up to a profile. Activity and message history stay visible for 30 days.
Unlock external sends for $10. That's the minimum funds purchase—enough to send to real subscribers whenever you're ready. Top up manually or set funds to auto-refill.
Questions before you ship
Every external send to someone who isn't a verified test user—on email, in-app, push, or webhook. Sends to verified test users are zero-rated and never count. Rate: $0.40 per 1,000 messages, flat across channels.
From first send through IPO
Start on pay-as-you-go and stay on Customer.io as you grow—no re-platforming, no migrations, no starting over.
Ready for more? Essentials has you covered.
When you're ready to move beyond transactional sends—think multi-channel campaigns, behavioral workflows, and marketing automation—Essentials is the natural next step. Everything you've built carries over, no migration required.
Infrastructure for how builders actually work
Transactional email
Receipts, password resets, and notifications—sent reliably via API or MCP, without a bloated dashboard in the way.
AI agents
Give your agent a messaging layer. Trigger transactional emails and notifications from any MCP-compatible environment, with full delivery visibility.
Early-stage products
Get messaging working on day one. No $100/month commitment until you're ready to scale into behavioral workflows.
Product releases
Announce new features to up to 5,000 users the moment you ship. Send one-off broadcasts directly from Customer.io—no lifecycle setup required.
Trusted by teams at every stage
As a data company, we understand the importance of keeping your company’s data secure. Stay compliant with GDPR, HIPAA, SOC 2 Type II, CCPA, and other regulations.
Set rules to proactively block restricted personal data.
Keep data safe by restricting access by user role.
Get started with your agent
Paste this into Claude, Cursor, or any MCP-compatible agent. It'll sign you up, verify your domain, and send your first message—no tabs required.
Goal: get me from nothing to a test email in my inbox using Customer.io's Builder plan. 1. Create my Builder account. 2. Send me a transactional "hello" email. 3. Show me the delivery record. Install the `cio` CLI with `npx skills add customerio/cio-cli`. Run `cio prime` first and consult the relevant `cio skills` for the workflow.