The Best Calendar APIs | For Developers, Startups, and SaaS

Our team has worked with the major calendar providers, Google Calendar, Outlook, and iCloud Calendar, for years. During that time, we built our own calendar API integrations for every provider and learned how hard it is for a new startup or an existing company to integrate calendars into their product.

Integrating calendar providers is hard because each provider offers its own API, and these APIs are different from each other. To add Outlook and Google Calendar to your software, you need to implement two separate APIs, each with its own rules and limitations.

In this article, we list the best calendar APIs that make it easier to integrate all calendar providers into your application.

Why does using the right calendar API matter?

Although most users use Google Calendar, there is still a very large group of users on Outlook Calendar, iCloud, or a mix of all three, depending on their job and personal preferences.

This is why it is important to support all major providers when you build an application, a SaaS product, a startup centered on calendars, or simply a feature that lets users connect their calendar.

The good news is that Google Calendar, Outlook, and iCloud Calendar all offer public and free APIs to work with a user's calendar. Through these APIs you can read a user's events and create, update, or delete events, depending on your use case.

The downside of integrating several calendar providers is that they do not follow the same API conventions. Developers need to implement each provider separately, which is expensive, because every provider has a different API with its own instructions and edge cases.

On top of the initial implementation, you also need to maintain each integration, since calendar providers change their APIs from time to time.

With the right calendar API, your company can integrate every calendar provider through a single API. This reduces development and maintenance costs and, most importantly, lets you ship features faster.

What are the best calendar APIs?

1. Apiroc

Apiroc is a Unified Calendar API built by a team that has worked with all major calendar providers for years. We built calendar integrations that handle billions of API calls, and we realized we could offer a simpler and more affordable unified calendar API to the market.

The proposition is simple: Apiroc lets you integrate Google Calendar, Microsoft Outlook (Office 365, Exchange, Outlook.com), and Apple iCloud Calendar through one API. There is no need to learn and implement multiple APIs or to deal with each provider's edge cases and gotchas.

Leave the maintenance to us and focus on shipping faster and growing your user base.

Features

• One API for Outlook, Google Calendar, and iCloud Calendar : Apiroc offers a single API for all major calendar providers, so you can integrate every provider in a short amount of time without coding or maintaining each one separately.
• Support for all major calendar operations : The Apiroc Unified Calendar API is designed for all types of applications, from calendar apps and scheduling tools to CRMs, HR systems, and AI agents. It supports creating, reading, updating, and deleting events, attendees and RSVPs, recurring events with single-instance changes, custom metadata, conferencing links, and free/busy availability across calendars and providers in one request. The API is unified, so you get the same endpoints and the same behaviour for every provider.
• Calendar API that's easy to get started and integrate : Right after you sign up, you get a short list of steps to integrate the API into your codebase. Authentication uses a simple API key, end users connect Google and Microsoft through a hosted OAuth flow, and iCloud connects with an Apple ID and an app-specific password, with no OAuth setup needed.
• Documentation, SDK, and Postman Collection : Apiroc has concise documentation, an official Node.js SDK, an example application on GitHub, and a Postman Collection that lets you try the API and its capabilities right away.
• Reliable and well supported : Apiroc runs on infrastructure that has processed billions of calendar API calls, with automatic retries, provider rate limit handling, and failover. Our team has worked with calendars for years and will do its best to help you with any issue or request.
• Support for Webhooks : You do not need to integrate webhooks for each calendar provider. Apiroc sends your app real-time, signed webhook notifications for changes in Google and Microsoft calendars. Webhooks for iCloud Calendar are planned.

Supported Calendar Providers

• Google Calendar
• Outlook Calendar
• iCloud Calendar

Pricing

Apiroc has a free plan with up to 10 End User Accounts, unlimited API requests, webhooks, and metadata for non-production use. The Pro plan costs $25 per month, includes 50 End User Accounts, and then costs $0.50 per additional End User Account per month, with production use and 300 requests per second. Enterprise plans offer custom pricing, volume discounts, and custom rate limits. An End User Account is one connected provider account (for example one Google account), which can contain multiple calendars.

2. Nylas Calendar API

The Nylas Calendar API is a scheduling-focused platform made for developers who want to build custom scheduling solutions without worrying about the different calendar providers.

Features

• Personalized workflows : With the Nylas Calendar API, you can configure scheduling workflows that fit your use case.
• Support for webhooks : You receive real-time notifications when events are scheduled.
• Easily ship one-on-one, collective, or round robin scheduling : The Nylas Calendar API makes it easy to build one-on-one scheduling, as well as more complex cases like round robin scheduling.
• Native scheduling components : The Nylas Calendar API offers native scheduling components that you can embed into your website and customize to match your brand.

Nylas Calendar API downsides

The main downside of the Nylas Calendar API is its heavy focus on scheduling. If you simply want to integrate multiple calendars into your application, or your use case does not revolve around embedding scheduling, an alternative like Apiroc might make more sense.

3. Cronofy Calendar API

Like Nylas, Cronofy offers calendar APIs for companies that need scheduling features in their applications.

Features

• Embedded Scheduler : You can easily embed a fully managed scheduler into your application. The scheduler can be a button that opens a modal where the user books the meeting.
• Workflows Support: Cronofy notifies you when someone books, reschedules, or cancels a meeting. You can also receive these changes via webhooks.
• Customizable UI : The embedded scheduler can be white labeled to match your company brand.

Cronofy Calendar API downsides

The Cronofy Calendar API is great for building custom scheduling solutions and white labeling them to match your branding, but it has its shortcomings when you build solutions that are not scheduling-specific.

4. Cal.com API

The Cal.com API lets developers and companies add scheduling to their apps with customizable components.

Features

• Atomic components : You can use the Cal.com atomic UI components to build your scheduling feature or platform. A component can be as simple as the “Connect Google Calendar” button or as complex as the “Booking Form” where the user picks a time to meet.
• Support for payments : You can integrate Stripe to collect payments for your bookings.
• Customizable UI : Besides being modular, the components can also be customized to match your brand.
• Ready to use in React.js : The Cal Atoms can be used in React.js by simply installing the "@calcom/atoms" package.

Cal.com API downsides

One downside of Cal.com is that it focuses on giving developers the most straightforward way to build scheduling solutions. If you want a scheduling-agnostic calendar API that talks to all calendars, Apiroc might be the better choice.

5. Calendly API

Calendly is the most popular appointment scheduling solution, used by millions of students, professionals, and companies. Through the Calendly REST API, you can embed your Calendly scheduling links into your website, share meeting links, view availability data, and more.

Features

• Event automations : You can subscribe to Calendly webhooks to get notified when invitees book, cancel, or reschedule meetings.
• Embed scheduling pages : You can embed your Calendly booking pages into your app and customize the look and feel.
• Get event and invitee data via API : You can make POST requests to the Calendly API to receive event or invitee information in real time via webhooks. You can also make GET requests to retrieve event information.
• View Availability : Via the API, you can retrieve a list of all available times for a specific event type, calendar, or user.

Calendly API downsides

The Calendly API is focused on managing Calendly event types, booking information, and availability. It is not meant to unify multiple calendars in one API or to build complex custom solutions.

6. Google Calendar API

Compared to the other calendar providers, Google Calendar has the best calendar API in terms of conventions, documentation, and overall ease of implementation.

Using the Google Calendar API, you can read, create, update, and delete calendar events, get availability, and more. The API works with single and recurring events, and has great support for features like reminders and invites.

Features

• Easy to use and implement : Google has nailed the API design. The endpoints are easy to understand and quite reliable.
• Support for CRUD : You can do almost everything you do in the Google Calendar interface through the API.
• Support for webhooks : Google Calendar notifies you when a calendar changes, so you can react to that information.
• Support for extended properties: Depending on your use case, you might want to enrich Google Calendar events with custom data. Extended properties let you store that data without keeping it in your own database.

Which Calendar API should you use?

The best calendar API depends on your use case and requirements.

If you want to integrate all calendar providers through a single API, Apiroc is your top pick.

If you need a scheduling-specific API with the ability to embed a calendar or scheduling form, Nylas and Cronofy are your top choices.

If you simply need to embed a booking form into your website, you can try the Cal.com or Calendly APIs, as both offer ways to embed and customize the booking experience.

Use Apiroc

Apiroc is one of the most affordable Unified Calendar API products available in 2026. The free plan includes up to 10 End User Accounts with no credit card required, and the Pro plan starts at $25 per month. You can get started for free, try the API, and upgrade when you are ready for production.