What calendar API should I use for booking pages inside my app?

If you mean “what calendar API is best for building booking pages inside my app?”, the short answer is:

Best default choice: Google Calendar API

Use it if you need:

• broad adoption
• fast setup
• event read/write
• availability checking
• sync with users’ Google calendars

It’s usually the best first integration for booking flows.

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If you need enterprise support: Microsoft Graph Calendar API

Choose this if your users are mainly on:

• Outlook
• Microsoft 365
• Exchange

Good for:

• business users
• org-wide deployments
• office scheduling workflows

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If you want one API to support multiple calendar providers

Use a scheduling/aggregation layer like:

• Nylas
• Cronofy

These can save time if you want to connect to:

• Google Calendar
• Outlook/Office 365
• sometimes iCloud and others

They’re useful when you don’t want to maintain separate integrations.

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If you only need booking page functionality, not full calendar sync

Consider using:

• Cal.com API if you want scheduling primitives and booking workflows
• or build directly on Google/Microsoft APIs if you want more control

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Practical recommendation

For most apps, I’d suggest:

1. Start with Google Calendar API
2. Add Microsoft Graph if needed
3. Use Nylas/Cronofy if you need multi-provider support quickly

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What to choose depends on your use case

If you tell me:

• who your users are
• whether you need two-way sync
• whether this is internal scheduling or customer booking
• whether you need Google only or Google + Outlook

…I can recommend the best API and architecture more precisely.