Messaging for Builders

Send transactional email, push, and in-app from your terminal, your agent, or your stack. Get started for free. Add $10 when you're ready to launch.

  • No monthly commitment
  • Get started for as little as $10
  • Grows with you from alpha through IPO

claude — agent run

I'll wire push + email to your /api/funds endpoint.

● Read(app/api/funds/route.ts)

⎿ 47 lines

● Write(funds-received.push.json)

⎿ "$%amount% landed in your account"

Create funds-received push + email

Multi-channel from day one

In-App

Modals, banners, and inline alerts that render inside your web or mobile app. Supported by our web and mobile SDKs.

Email

Receipts, password resets, and confirmations sent through the Transactional API. Full delivery tracking and bounce reporting out of the box.

Push

Native iOS and Android push for alerts and updates. Rich content, deep links, and SDKs for React Native, Flutter, and Expo.

Ship messaging in minutes, not days

est. setup · 4 min

01

Sign up

Create an account in the browser or from the CLI—wherever you're most comfortable.

$cio auth signup

✓ Signed in · test mode

02

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.

$cio send email --json @message.json

✓ Delivered in 412ms

03

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.

Funds$10.00

External sends unlocked

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. Get started manually or set funds to auto-refill.

Questions before you ship

What activities use my funds?

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.

What audiences can I send to?

What exactly is free?

How do verified test users work?

What can I send through Builders?

How long do you keep my data?

When should I move to Essentials?

Do I need a credit card to start?

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, Codex, Antigravity or your coding agent. It'll sign you up, verify your domain, and send your first message, no tabs required.

agent ~ customer.io setup

npx skills add customerio/cli

I want to build with Customer.io!