One API for all calendars
Unified Calendar API
For over three years, we've synchronized hundreds of millions of events across iCloud, Outlook, and Google Calendars, and we know the pain of dealing with multiple calendar APIs. Our Unified Calendar API combines years of trial and error to make it possible to communicate with iCloud, Outlook, and Google Calendar using a single API.
Syncs Executed
50+Million
Events Synced
800+Million
API Success Rate
99.9%
Why use the OneCal Unified Calendar API?
We've been ironing out our calendar synchronization algorithms for years, ensuring events can be synced across all major calendar providers. As a result, we've built a Unified Calendar API that's very reliable and proven to work across thousands of calendars and millions of events.
Support for iCloud, Outlook and Google Calendar
Our Unified Calendar API works with iCloud, Outlook, and Google Calendar, ensuring you focus on shipping fast and growing your company instead of figuring out the gotchas of each calendar provider.
Proven to be reliable
OneCal is at the forefront of the calendar synchronization space, helping thousands of professionals and companies automatically sync their calendars in real-time. Our Unified Calendar API is the result of hundreds of thousands of events being synced across all major providers, and our customers are always happy with the service.
Easy to Use & Build on Top
Our Unified Calendar API is designed to help you integrate all calendar providers into your application. You can use our Unified Calendar API to simply integrate a calendar provider into your application, add scheduling functionality into your app, or even build a calendar app. Our Unified Calendar API makes it a breeze to build everything on top of a third-party calendar API.
Real-Time Calendar Webhooks
OneCal handles webhooks from every major calendar provider and converts them into a simple, consistent event format. Your app receives changes instantly, so your users never see outdated schedules. No polling, no messy integrations, no missed updates.
One API for all calendars
Integrate all calendars in your app
Integrate iCloud, Outlook and Google Calendar into your app with a single API. Add scheduling, sync events, or build a full calendar experience, all without the complexity of managing multiple APIs.
- Bring your existing calendars.
Already manage calendar accounts? Just bring your existing API keys, no re-authentication required.
- No vendor lock-in.
You can easily switch to a different calendar provider if you want to. It's as easy to export your calendar accounts as it is to import them.
- Built to scale.
Our Unified Calendar API is designed to be scalable and easy to use. You can scale your application to handle millions of users and events.
Predictable Pricing
Our pricing is designed to be predictable and transparent. Volume discounts available for large organizations.
Free
The essentials to start testing the API.
Free
Start for free- Up to 10 End User Accounts
- Non-production use
- Unlimited API Requests
- 20 API Requests per second
- Webhooks API
- Calendar Event Metadata
- Standard Support
Pro
A plan that scales with your rapidly growing business.
$25/month
Start for free- 50 End User Accounts included, then $0.50/EUA/month
- Production use
- Unlimited API Requests
- 300 API Requests per second
- Webhooks API
- Calendar Event Metadata
- Priority Support
Enterprise
Custom pricing for large organizations.
Custom
Get in touch- Everything in Pro
- Volume discounts
- Custom rate limits
- Dedicated support
- Dedicated Slack channel
- Custom Features
Unified Calendar API FAQ
- What is the Unified Calendar API?
- A Unified Calendar API allows developers to integrate multiple calendar providers (Google Calendar, Outlook, iCloud, etc.) into their applications with a single, consistent interface.
- Which calendar providers are supported?
- We support Google Calendar, Microsoft Outlook (Office 365, Exchange, Outlook.com), and iCloud.
- Who is this API for?
- It's designed for SaaS applications, productivity tools, CRMs, booking platforms, HR systems, and any app needing seamless multi-calendar integration.
- Do you provide SDKs or client libraries?
- Yes, we offer an SDK for Node.js. SDKs for Python, PHP, and Java are coming soon.
- How do I authenticate calendar users?
- We use OAuth 2.0 for Google and Microsoft and App-Specific Passwords for iCloud.
- Can I create, update, and delete calendar events?
- Yes, you can CRUD (Create, Read, Update, Delete) events across all supported calendars.
- Do you support recurring events?
- Yes, we fully support recurring events, including modifications to individual occurrences.
- Is there a free plan?
- Yes, we offer a free tier with limited API calls. Paid plans provide higher limits and premium support.
Build Your Next App with Our Unified Calendar API
With the OneCal Unified API, you'll spend time building features that really matter and leave the tedious calendar APIs across all your calendar providers to us.