> This page is part of the [Customer.io documentation](https://docs.customer.io). For the complete index, see [llms.txt](https://docs.customer.io/llms.txt). > Last updated: May 6, 2026 # Builder plan: pay-as-you-go The Builder plan provides messaging infrastructure for early stage builders and transactional senders: set up and test your messaging for free, go live for $10, and upgrade to the full platform when you’re ready! ## How it works[](#how-it-works) The Builder plan is a low-cost way to set up and start sending [transactional messagesMessages that your audience implicitly opts into—like purchase receipts, password reset requests, shipping updates, two-factor authentication codes, etc.](/journeys/transactional-api/) and one-time broadcasts with Customer.io. You can send emails, push notifications, in-app messages, and webhooks via our CLI, MCP server, or web app. You can also send [SMS](/journeys/sms-get-started/#set-up-sms-through-twilio) and [WhatsApp](/journeys/whatsapp-get-started/#set-up-twilio) if you integrate with Twilio. Unlike our other offerings, the Builder plan is not a subscription model and has no monthly fees, no trial periods, and no send limits. It’s free to build and test! When you’re ready to send to your customers, you add funds, starting at just $10, and pay $0.40 per 1,000 messages. To create marketing campaigns or set up out-of-the-box integrations with services like Salesforce, check out our [subscription-based plans](https://customer.io/pricing/) instead. ### Who is the Builder plan for?[](#who-is-the-builder-plan-for) Anyone can sign up for the Builder plan, but it’s intended for: * **Developers and founders at startups** in the early stages who need reliable transactional messaging and aren’t yet ready to sign up for a monthly plan. * **Mobile developers** who want to test push notifications and in-app messages before committing to a monthly plan. * **AI-native builders** working with LLMs, agents, and other tools who want messaging as infrastructure. You don’t need a GUI; you use our CLI or MCP server to support your workflows.  If you need behavioral workflows, audience segmentation, or multi-channel automation, start with the [Essentials plan](https://customer.io/pricing/). ### What’s included in the Builder plan[](#whats-included-in-the-builder-plan) The Builder plan includes the following features. Those not included are available on our [Essentials and higher plans](https://customer.io/pricing/). Workflows Available in Builder Plan [Transactional messagesMessages that your audience implicitly opts into—like purchase receipts, password reset requests, shipping updates, two-factor authentication codes, etc.](/journeys/transactional-api/) [Broadcasts](/get-started/send-messages/#newsletters) (Newsletters only) [API-triggered broadcasts](/get-started/send-messages/#api-triggered-broadcasts) [Campaigns](/get-started/send-messages/#campaigns) Message channels Available in Builder Plan Details Email Send for free to up to 10 [verified recipients](#add-test-users) before sending to customers. Up to 2 sending domains per workspace. Push notifications [In-app messages](/journeys/send-in-app-message/) [Inbox messages](/journeys/inbox-setup/) Webhooks [SMS or WhatsApp through Twilio](/get-started/set-up-messages/#set-up-smsmms) SMS or WhatsApp through direct integrations LINE Slack Anonymous in-app messages Data and integrations Available in Builder Plan Details [People](/get-started/add-people/) Add verified, test recipients and customers to your workspace. [Manual segmentsA segment of people you maintain manually. You must explicitly add people to, or remove people from, the segment.](/journeys/manual-segments/) [Dynamic, data-driven segments](/get-started/segments-and-people-data/#data-driven-segments) [Custom objectsAn object is a non-person entity that you can associate with one or more people—like a company, account, or online course.](/journeys/objects/) Mobile SDKs and libraries Native integrations for services like Salesforce or Hubspot Analytics across workflows and message channels ## Set up & test your account[](#set-up--test-your-account) If you’re new to Customer.io, you can [sign up for the Builder plan here](https://fly.customer.io/signup?signupType=builder) or through [our CLI](/ai/cli/get-started/). You can sign up without payment information and start setting up your message channels and integrations right away. Dive in and get started! ### Should I integrate via Customer.io’s MCP or CLI?[](#should-i-integrate-via-customerios-mcp-or-cli) CLIs are optimized for agentic communications and developer-oriented use cases. Our CLI helps you build workflows and automations from your terminal. You use this in conjunction with terminal-based coding agents like Claude Code or Codex. If you want to send messages by interacting with a third-party agent interface, like Claude Desktop or ChatGPT, you’ll want to integrate via MCP instead. This is typically for marketers or others who aren’t primarily developers. This way you have a GUI to interact with, rather than the command line. ### Authenticate via CLI[](#authenticate-via-cli) If you signed up through our CLI, you’ll already have a key and can skip this step. If you signed up through our site, go to *Home* in your workspace to create a *Service Account API key*. Learn more about [getting started with our CLI](/ai/cli/get-started/). ### Authenticate via MCP[](#authenticate-via-mcp) To get started with our MCP server, go to [*Personal Settings > MCP*](https://fly.customer.io/settings/personal) and follow the instructions for your client of choice. You can [find more info in our docs](/ai/mcp-server/) too. ### Set up your message channels[](#set-up-your-message-channels) If you plan to send emails, add your sending domain to your workspace to start the verification process. Your domain must be verified to send emails to anyone, including your [verified recipients](#add-test-users). Otherwise, you can set up other message channels through our CLI, MCP server, or [Workspace Settings](https://fly.customer.io/workspaces/last/settings). ### Add verified recipients[](#add-test-users) Verified recipients are test users that have opted into receiving emails from you. You can add up to 10 verified recipients to your workspace. Account Admins are automatically added as verified recipients. Verified recipients are only available on the Builder plan. #### Add recipients from *Home*[](#add-recipients-from-home) When you add a verified recipient from *Home*, this person automatically receives an email asking them to opt-in to receiving emails. You can’t send to verified users until they’ve opted in. #### Add recipients from the People page[](#add-recipients-from-the-people-page) You can also add individuals or groups of people via CSV from the People page. After you add people, select each person you want to verify. Then choose **Actions > Invite verified recipient** to send them an opt-in confirmation email. #### Check opt-in status[](#check-opt-in-status) To check whether your verified recipients have opted-in to receiving emails, review their profile: 1. Go to *People*. 2. Search for and select your recipient. 3. Check *Verified user status*. `Pending` means they have not opted in yet. `Verified` means they have opted in and can now receive emails. ### Send to verified recipients[](#send-to-verified-recipients) Send emails to verified recipients to check how your emails look before going live. Your sending domain must be verified before you can send to anyone, including verified recipients. ## Send to customers: add funds[](#send-to-customers-add-funds) When you’re ready to send to your customers, you purchase funds to go live. Funds don’t expire, and you can track usage from *Home* or your [Plans & Billing page](https://fly.customer.io/settings/billing/your-plan). Details **Minimum purchase** $10 (~25,000 sends) **Maximum funds per purchase** $1,000 **Cost** $0.40 per 1,000 messages **Message rate** Flat across all channels—email, in-app, push, webhooks, and SMS or WhatsApp through Twilio **Profiles** Unlimited people profiles, no objects 1. Click **Add funds**. 2. Enter your payment information and the amount you want to purchase. The minimum purchase is $10, and you can add funds at any time.  Sending stops when your funds run out When your funds run out, sending stops and you need to add funds manually. We’ll email your Account Admins when you’re low on funds so you know to take action. ## Manage your plan[](#manage-your-plan) If you’re new to Customer.io, you can [sign up for the Builder plan](https://fly.customer.io/signup?signupType=builder). Otherwise, learn more about upgrading and downgrading below. You can upgrade to Essentials or higher by reaching out to our team at [win@customer.io](mailto:win@customer.io). When you upgrade, everything you’ve built carries over—your message channels, profiles, and content. No migration is required. To downgrade from another plan, you’ll also reach out to our team at [win@customer.io](mailto:win@customer.io).