You drop a Calendly link into your product and booking works in an afternoon. Then a customer asks why the flow leaves your app, why it can’t read availability from their own connected calendar, and why the booking confirmation doesn’t match your brand. Now you’re fighting an embed you don’t control. The question stops being “which scheduling tool” and becomes “do I embed someone else’s UI or build scheduling I own.” This page compares both, with the real endpoints for each.
What are the best alternatives to Calendly for building scheduling integrations?
Section titled “What are the best alternatives to Calendly for building scheduling integrations?”The best alternative for building, not embedding, is a scheduling API that exposes availability and bookings as raw endpoints. Calendly is a finished product with an embed and an API focused on reading scheduled events and event types, not on building a custom booking surface. The Nylas Scheduler API gives you POST /v3/calendars/availability for open slots and POST /v3/scheduling/bookings to create them across every supported calendar provider, so you own the UI.
Most “Calendly alternatives” are also finished products: Cal.com, SavvyCal, Acuity. They compete on features and price, not on whether you can build a custom flow. If your goal is a scheduling experience that lives inside your product, reads each user’s connected Google or Microsoft calendar, and writes events you control, you want an API layer underneath the booking logic. The Scheduler API and availability endpoint give you that, and the same grant reaches Google, Microsoft, iCloud, and Exchange calendars without a second integration.
Embed Calendly vs build with the Scheduler API
Section titled “Embed Calendly vs build with the Scheduler API”Embedding Calendly is the fastest path to a working booking page, and for many teams it’s the right call. Building with the Scheduler API takes more code up front but removes the per-seat pricing, the off-domain redirect, and the ceiling on what you can customize. The table below maps the two approaches against the work scheduling actually requires.
| Task | Embed Calendly | Build with Nylas Scheduler API |
|---|---|---|
| Time to first booking page | Minutes, paste an embed | Hours, create a configuration plus UI |
| Who owns the booking UI | Calendly’s widget and domain | Your app, your domain, your styling |
| Read user’s own calendar | Organizer’s Calendly account only | Any connected grant via POST /v3/calendars/availability |
| Create the booking | Calendly does it internally | POST /v3/scheduling/bookings, you control it |
| Provider coverage | Google, Microsoft, others | Google, Microsoft, iCloud, Exchange |
| Pricing model | Per-seat subscription | Per-grant API usage |
Both read a calendar and write an event. The difference is ownership: an embed hands you a UI you can’t change, while the API hands you primitives you assemble across every supported calendar provider. Teams that start with the embedded Nylas Scheduler component get Calendly-style speed and can drop to the raw API later without rebuilding.
Which Calendly alternatives offer the most flexible API for custom scheduling?
Section titled “Which Calendly alternatives offer the most flexible API for custom scheduling?”The most flexible option exposes availability and bookings as separate, callable endpoints, not a single embed. Calendly’s API reads scheduled events and event types but can’t compute availability across an arbitrary user’s connected calendar. The Nylas availability endpoint accepts multiple participants, working hours, buffers, and an availability_method of collective or max-fairness, so you script the exact booking logic you need.
Flexibility shows up in the request body. A POST /v3/calendars/availability call takes participants with per-person open_hours, a start_time/end_time window in Unix timestamps, duration_minutes (a multiple of 5), interval_minutes for slot spacing, and an availability_rules object with buffer and default_open_hours. That’s the math a round-robin or collective meeting needs, returned as open slots in one response. Calendly surfaces none of those knobs through its API. For the full parameter set, see check availability.
How do I compute availability across a user’s connected calendar?
Section titled “How do I compute availability across a user’s connected calendar?”Send a POST /v3/calendars/availability request with the participants and a time window. The endpoint reads each connected calendar, intersects busy times, and returns only the slots when everyone is free. The path takes no grant because participants are identified by email, and every address must map to a valid Nylas grant. The duration_minutes value must be a multiple of 5.
The request below finds 30-minute slots for two participants inside a working-hours window. It does the cross-calendar intersection Calendly handles internally, but here you get the raw slots back to render however your product needs. The round_to field snaps slot start times to a clean boundary, 15 minutes in this example.
curl --request POST \ --url 'https://api.us.nylas.com/v3/calendars/availability' \ --header 'Accept: application/json' \ --header 'Authorization: Bearer <NYLAS_API_KEY>' \ --header 'Content-Type: application/json' \ --data '{ "start_time": 1600890600, "end_time": 1600999200, "interval_minutes": 30, "duration_minutes": 30, "round_to": 15, "participants": [ { "email": "[email protected]", "calendar_ids": ["[email protected]"] }, { "email": "[email protected]" } ], "availability_rules": { "availability_method": "collective", "buffer": { "before": 15, "after": 15 } } }'Once you have the slots, you either render them yourself or let a configuration drive a booking page. For a multi-host walkthrough with buffers and time zones, read check availability.
How do I create a booking the way Calendly does internally?
Section titled “How do I create a booking the way Calendly does internally?”Save the booking logic once as a configuration, then create bookings against it. A POST /v3/grants/{grant_id}/scheduling/configurations request stores who can be booked, which calendar to check, the meeting duration, and event details, and returns a configuration_id. From there, a POST /v3/scheduling/bookings request creates the actual booking, which is the step Calendly performs behind its widget.
The configuration is the reusable object every booking references, so you create it once and reuse the ID across pages. The request below registers an organizer, points availability at their primary calendar, and sets a 30-minute slot. Storing this server-side keeps your booking rules in one place instead of duplicated per page.
curl --request POST \ --url 'https://api.us.nylas.com/v3/grants/<NYLAS_GRANT_ID>/scheduling/configurations' \ --header 'Accept: application/json' \ --header 'Authorization: Bearer <NYLAS_API_KEY>' \ --header 'Content-Type: application/json' \ --data '{ "participants": [ { "email": "[email protected]", "is_organizer": true, "availability": { "calendar_ids": ["primary"] }, "booking": { "calendar_id": "primary" } } ], "availability": { "duration_minutes": 30 }, "event_booking": { "title": "30-minute meeting" } }'To prevent two guests grabbing the same slot, the managed booking flow rejects a second claim for you. The race condition and the do-it-yourself guard are covered in prevent double-booking.
When is embedding Calendly the right choice?
Section titled “When is embedding Calendly the right choice?”Embed Calendly when scheduling isn’t core to your product and you want it live today. For a sales booking link, a support handoff, or a side feature, an embed beats building. You paste one snippet, the organizer manages their own availability, and you write zero scheduling code. For a low-volume use case, the per-seat cost beats the engineering hours.
The build case wins when scheduling is the product or a key surface inside it. The moment you need the flow on your own domain, availability from each user’s connected calendar (not just the organizer’s), branded confirmations, or booking data in your own database, an embed becomes a wall. At that point the Scheduler API and the availability endpoint give you the primitives across every supported calendar provider, and the embedded component is there if you want a head start before going fully custom.
What’s next
Section titled “What’s next”- Embed a scheduling page for the fastest, Calendly-style path with the Nylas Scheduler component
- Check availability for working hours, time zones, buffers, and availability methods
- Prevent double-booking for the concurrency guard the managed flow gives you
- Using Nylas Scheduler for configurations, sessions, meeting types, and reminders