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A diagram showing the different types of notifications: SMS, in-app messages, push notifications, and email

A Developer’s Guide to Notification APIs

Donnie Wang

July 10, 2023

While marketing-related notifications are often handled by marketing automation platforms, engineering teams require notification infrastructure that is designed for automated product-driven notifications. This might be a simple SMS password reset notification or new user onboarding email sequence. Or it may be a more complex notification tied to a feature of the application, such as an approval request sequence.

The infrastructure required to handle these notifications is extensive. Logic is typically required to trigger on an event, follow a specific workflow, personalize content, follow compliance guidelines, respect user preference, and work intelligently across channels (eg. email, SMS, push, in-app inbox, chat, etc). And it may require advanced send logic such as batching, digesting, throttling, and scheduling of notifications.

This is precisely what notification APIs solve. A notification API is a combination of backend infrastructure and both server- and client-side SDKs that enable developers to build notifications in web and mobile apps. It's free to signup and try Courier, the leading Notification API, yourself. Otherwise, read on to learn more.

Rather than developers spending time and effort building and maintaining the infrastructure on their own, Notification APIs give developers everything they need to create optimized, product-driven notifications that users will open and interact with.

Notification APIs are used together with communication APIs like Twilio, Messagebird, Slack, and FCS—acting as an abstraction layer to enable notification use cases. As a result, integrating notifications into an application and maintaining that infrastructure becomes a swift and future-proof process.

In this guide, we delve deeper into notification APIs, their role in transactional and marketing notifications, practical use cases, and the indirect benefits they offer.

Understanding and using notification APIs

Here are some examples of Notification API features. These are capabilities that add notification capabilities to communication APIs such as Twilio, Microsoft Teams, MessageBird, Slack, and so on.

Multi-channel send: Notification APIs allow for dispatching notifications across multiple channels, like email, SMS, and push notifications. This frees developers from the complexities of maintaining individual infrastructures for each channel, streamlining the process considerably. For instance, an HR application might dispatch a job offer requiring a signature via SMS, a channel offering urgency and external reach, while using a tool like Slack—an internal, less urgent channel—for onboarding tasks with a new employee.

Delivery status awareness across channels: A unique feature of notification APIs is their ability to track delivery status across all channels. This means, if an email, SMS, or push notification has been successfully delivered, it's accurately logged and reported. This insight enables developers to understand the efficacy of their communication across different platforms.

Additionally, some sophisticated notification APIs also monitor “read statuses.” This means that when a user reads a notification on one platform, it can potentially halt the delivery or alter the display of notifications on other channels, for example marking them as opened or read.

Automations: From fetching the latest data for inclusion in a notification to setting up advanced delivery timings and rules across channels, notification APIs automate much of the orchestration process. Automations within notification APIs reduce manual effort and potential errors. This might involve sending a time-delayed, multi-channel sequence of notifications that stop as soon as the user reads them. Alternatively, it could involve digesting and batching frequent notifications based on preset or user-defined frequency or even throttling messages that trigger too often.

Template management: Many notification APIs offer tools for developers to efficiently design, manage, and repurpose notification templates across various channels. These include pre-made templates as well as the option to create your own, eliminating the necessity of crafting notifications from scratch every time. This allows developers to focus more on the message and its intended impact, enhancing efficiency and overall user engagement.

Central logs and reporting: Robust logging and reporting capabilities are integral to notification APIs. This is especially relevant for notifications because it can present delivery status across channels in a single view. These features provide invaluable insights and aid in troubleshooting.

User preferences: Notification APIs provide a simple way to collect and respect user preferences for notification topics, channels, and frequencies, ensuring notifications don’t overwhelm users. Eg. a user might want to receive billing notifications via both SMS and email. But they may want to receive system error notifications via PagerDuty. And they may want to hold all comments on a project, to be rolled up into a single email digest every week. All of this is possible with a Notification API, which provides both the frontend components for the UI as well as the backend logic to respect these preferences. If all notifications get sent through a notification API, the service becomes a useful tool for controlling users’ notification preferences.

Web and mobile notification center (Inbox): In addition to external channels like email, Slack, and SMS, it often makes sense to hava a notification center, or "inbox" that lives inside of the web or mobile app. This typically also includes a bell icon with a change badge that counts number of messages, as well as related push notifications. A notification API will not only handle all the back-end logic for this functionality, but it will typically also offer a complete set of web and mobile SDKs for building the frontend experience. This allows developers to construct a fully functional in-app inbox and preference center with a notification API, elevating the overall user experience with minimal additional development time. Here's an example of Courier's inbox offering.

Internationalization: Notification APIs offer the advantage of internationalization. If the API manages message templates, it’s possible to select a template appropriate for each user’s region and language or even work in sync with a translation API to serve translated versions of notification content. This ensures that each user receives personalized and localized notifications, further improving user engagement and satisfaction.

By leveraging a notification API, a developer can save time on building these features without sacrificing the end users’ experience or creating technical debt.

The role of notification APIs in transactional versus marketing notifications

A diagram summarizing transactional and marketing notification workflows

Notification APIs are typically used for transactional notifications. However, the transition away from moment-in-time marketing campaigns to ongoing Growth loops, is making Notification APIs more appropriate for marketing notifications than traditional marketing automation tools. To understand why that’s the case, let’s quickly define these two notification categories.

Transactional notifications are often triggered by user actions, such as making a purchase, resetting a password, or receiving a direct message. Or they may be tied to the functionality of a product feature - like a commenting feature in the app where you want to notify a person of an @mention. As their name suggests, these notifications are tied to specific transactions or interactions a user has with the application, playing a continuous role in user experience. They might rely on external channels like email and SMS or, for SaaS apps, they may be used with internal channels such as Slack, MS Teams, and PagerDuty.

Notification APIs prove particularly useful for transactional notifications due to their dynamic and event-triggered nature. By leveraging APIs, these real-time, personalized messages can be handled as they are generated, ensuring relevance.

On the other hand, marketing notifications are traditionally associated with promotional time-bound campaigns for a product, offer, or service. These messages focus on driving conversions or sales. Unlike transactional notifications, marketing notifications usually aren’t specific to the user or their activity in the app but instead get sent to larger groups of users. Marketing notifications also focus on external channels like email, SMS, push, and in-app.

Marketing notifications have traditionally been managed through a marketing platform due to their mass distribution nature and the connection to marketing campaigns. Specialized marketing platforms typically address the need for features such as opt-in logic to comply with anti-spam regulations, campaign management, and detailed analytics of the conversion process.

However, product growth experiments now cross the divide of marketing and are often more appropriate for Notification APIs than marketing automation tools. For example, if a user hits a key usage lifecycle milestone in your application, you may want to trigger a notification with a unique offer or with best practices to ensure their success. These kinds of notifications can drive higher application engagement and overall monetization of the app.

Over time, notification APIs have the potential to bridge the gap between transactional and marketing notifications. This potential stems from notification APIs’ ability to offer more personalized, event-driven marketing notifications that adhere to the user’s behavior and preferences.

In essence, notification APIs offer a robust framework that supports both transactional and marketing notifications, creating a cohesive and engaging user experience.

Benefits of using a notification API for developers

Notification APIs offer numerous indirect benefits that enhance efficiency, increase flexibility, and improve the developer experience.

One key advantage of notification APIs is provider independence. APIs abstract the underlying implementation details, allowing developers to switch providers (eg. from Postmark to SenGrid) swiftly if necessary without disrupting the overall application function. They can even provide failover between channels and providers without having to build out complex logic.

Notification APIs also offer consistency in notification formatting and delivery across various channels. Consistency improves user experience by ensuring each message is uniform, regardless of the channel through which it is sent.

From a developer’s perspective, APIs simplify the integration and management of notification systems. Developers don’t need to write boilerplate code for every new channel or message type or worry if their abstractions will carry over into a new provider’s API schema. Instead, they leverage the API’s functionality and use whichever providers they need, which can save considerable time and effort.

Sample use cases for notification APIs

Here are some examples of what you could build in your product using a notification API:

  • Status updates: Inform users about the progression of their initiated actions, such as “Your order is out for delivery” in a food delivery app context.
  • Appointment reminders: Remind users about upcoming appointments, deadlines, or important dates.
  • Approval requests: Request user approval for specific actions, such as document sharing or data access.
  • Authentication management: Handle password resets or two-factor authentication prompts.
  • Confirmation requests: Ask users to confirm potentially irreversible actions or decisions, such as deleting data.
  • Billing notifications: Inform users about upcoming payments, send payment confirmations, or notify them of billing issues.
  • Automated invites: Send automated invitations to events or cooperative endeavors.
  • Digests: Provide digests or summaries on user-selected topics at a frequency and channel set by the user.
  • E-commerce: Handle cart abandonment notifications, shipping updates, or requests for credit card updates.
  • Product engagement: Prompt users to return and complete a task, enhancing user engagement.
  • Survey requests: Solicit user feedback through surveys or review requests.
  • Welcome and user onboarding messages: Help new users get started with welcome messages and onboarding instructions.
  • Notify about a user’s activity: Alert users about new logins or changes to a shared project.
  • Platform engagement: Encourage users to engage with a platform or service more frequently.
  • Critical alerts: Notify users about critical issues, such as security alerts, product downtime, or other urgent matters.

In each of these use cases, notification APIs streamline the process of sending timely, relevant, and personalized notifications to users, enhancing user engagement and satisfaction.


Notification APIs have emerged as tools that enable developers to build product notification experiences that users love. By offering a streamlined way to manage notification content, delivery logic, internationalization, compliance, and user preferences, notification APIs reduce the complexity of building and maintaining the underlying infrastructure.

Notification APIs also help improve the user experience. By running all notifications through a single service, it’s possible to offer users more flexible preferences and cross-channel syncing of notification statuses. Prior to Notification APIs, only the largest, most sophisticated engineering teams could build this level of infrastructure in-house.

If you are interested in using a notification API, Courier is considered the leader in the market, funded by Twilio, Slack, and Google and used by companies such as Comcast, LaunchDarkly, Contentful, and Lattice. Courier is free to use for up to 10,000 notifications per month. Try it now or contact us to discuss your unique use case.

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Courier makes it easy to send SMS, email, push and in-app notifications with a single API call. We have a REST API, client SDKs and Docs that you'll love 💜


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