How to Subscribe to an ICS Calendar in Outlook

Outlook lets you subscribe to external calendars using ICS (iCalendar) URLs. If you want to add a team calendar, holiday schedule, or someone’s availability to your calendar, this guide covers how to do it in both Outlook web and desktop.

What is an ICS URL?

ICS is a standard calendar format. When someone shares a calendar via a URL (usually webcal:// or https://), you can subscribe to it in Outlook.

A few things to know about how it works:

• Read-only — you can see events but can’t edit them
• One-way — events flow from the source to your calendar only
• Slow refresh — Outlook checks every 12–24 hours
• No sync back — changes you make in Outlook won’t appear in the original calendar

Common ICS sources:

• Google Calendar public/shared calendars
• iCloud published calendars
• Team or department calendars
• Holiday schedules
• Sports team schedules
• Conference schedules

How to subscribe in Outlook web

1. Open Outlook (outlook.com or Office 365)
2. In the left sidebar, find Add calendar
3. Select Subscribe from web

4. Paste the ICS URL
5. Click Import

The calendar appears in your sidebar and events show up on your calendar view.

How to subscribe in Outlook desktop (Windows)

1. Open Outlook on your computer
2. Go to File > Open & Export
3. Select Internet Calendar Subscription

4. Paste the ICS URL
5. Click Add

The calendar is now subscribed and will refresh periodically.

Important: webcal:// vs https://

Outlook web requires https:// URLs, not webcal://. This is a common source of confusion.

If you have a webcal:// URL (common from Google Calendar):

• Change webcal:// to https://
• Example: webcal://calendar.google.com/calendar/ical/...%40group.calendar.google.com/public/basic.ics becomes https://calendar.google.com/calendar/ical/...%40group.calendar.google.com/public/basic.ics

Why the difference?

• webcal:// is a legacy protocol from the CalDAV standard (like http:// for web)
• Modern browsers and web apps (like Outlook web) require https:// for security
• Outlook desktop is more lenient and accepts both webcal:// and https://

In practice:

• Outlook web: Always use https://
• Outlook desktop: Can use either, but https:// is recommended
• Google Calendar: Provides webcal:// URLs by default, but you can convert them to https:// for compatibility

How to find ICS URLs from other calendars

From Google Calendar:

• Go to Settings > [Calendar] > Integrate calendar
• Copy the Secret address in iCal format (this is the webcal:// URL)
• Convert to https:// for Outlook web

From iCloud:

• In iCloud Calendar, right-click the calendar
• Select Share Settings
• Enable Public Calendar
• Copy the link

From a colleague’s Outlook:

• Ask them to go to Settings > Calendar > Shared calendars
• Have them select a calendar and choose Can view details or higher
• Copy the published ICS link

Limitations of Outlook ICS subscriptions

• Read-only — you can’t edit subscribed events
• Slow refresh — changes take 12–24 hours to appear
• No privacy controls — it’s all details or nothing
• One-way only — edits don’t sync back to the source
• Manual refresh — for frequently-changing calendars, this gets slow fast

This works fine for static calendars (holidays, conference schedules). For actively managed calendars, it falls short.

Better alternative: real-time sync with Hetk

If you use Outlook with Google Calendar or iCloud and want them to stay in sync automatically, Hetk offers real-time two-way sync that’s much faster than ICS subscriptions.

Hetk connects to all three providers (Google, Outlook, iCloud) via their official APIs and syncs events in seconds:

• Real-time — changes appear in seconds, not hours
• Two-way — edit in either calendar and changes sync back
• Privacy controls — mark events as private, show as busy only, or strip all details
• No duplicates — if the same meeting is in both calendars, you see it once
• Identity transform — synced events show your email as organizer
• Automatic — no manual refresh or management needed

Example: work Outlook, home Google

With ICS, you see your Google events in Outlook, but it’s read-only and updates take up to 24 hours. Create a meeting in Outlook, and Google Calendar doesn’t see it.

With Hetk, create an event in Outlook at work and it appears on your Google Calendar at home within seconds. Reschedule it in Google Calendar, and Outlook updates automatically.

Outlook web vs desktop

Hetk works with both:

• Outlook web (outlook.com or Office 365): Full support. All features work in the browser
• Outlook desktop (Windows or Mac): Full support
• Outlook mobile (iOS/Android): Full support. Changes sync in the background

ICS subscriptions work with Outlook web and desktop, but mobile support is inconsistent.

Pricing

Hetk’s Personal plan is $15/year ($10/year early adopter pricing) for unlimited calendars with up to 3 sync pairs, including a 21-day free trial.

Troubleshooting ICS subscriptions in Outlook

Calendar doesn’t appear after subscribing

Problem: The calendar doesn’t show up after you subscribe.

What to check:

1. URL format — Outlook web needs https:// URLs, not webcal://
2. Permissions — the source calendar must be publicly shared
3. Refresh — wait a few seconds after clicking Import, then check your sidebar
4. Browser cache — try refreshing the page or clearing cache

Outlook desktop shows “Error”

Problem: The subscribed calendar shows an error and no events appear.

Try these:

1. Right-click the calendar and select Refresh to manually retry
2. Delete and re-add the subscription with a fresh URL copy
3. Verify the URL is valid and the source calendar is still shared
4. Update Outlook (File > Office Account > Update Options)

Mobile doesn’t show subscribed calendar

Problem: The calendar shows in Outlook web but not on your phone.

Subscribed calendars sync to mobile with a delay. Wait a few minutes, then:

1. Close the Outlook app completely
2. Reopen it
3. Pull down to refresh

If it still doesn’t appear, the mobile app may not support ICS subscriptions.

Frequently asked questions

Does ICS work with new Outlook?

ICS subscriptions work with the modern Outlook (the cloud-based version released in 2024), both web and desktop. The process is the same as described above. If you have trouble, make sure you’re using the latest version.

Can I subscribe to a private Google Calendar?

No, ICS subscriptions only work with public calendars. Your private Google Calendar has a secret ICS URL, but if you share it with someone via ICS, they can see all your private events—there’s no privacy control. If you need to share a private calendar with limited visibility, use Hetk instead, which offers privacy controls to hide event details.

How do I remove an ICS subscription?

In Outlook web:

1. Find the calendar in your sidebar
2. Click the three-dot menu next to its name
3. Select “Delete calendar”

In Outlook desktop:

1. Right-click the calendar in your sidebar
2. Select “Delete”
3. Confirm you want to delete the subscription

The events will disappear from your calendar, but your own calendar data is unaffected.

Why is my subscription slowly getting out of sync?

ICS subscriptions “drift” when the source calendar updates frequently. You subscribe to a sports team’s schedule, the team reschedules a game, and your subscription doesn’t catch it for 24 hours.

This is why ICS subscriptions aren’t reliable for frequently-changing calendars.

When to use each approach

For active calendar management across multiple services, ICS subscriptions are a read-only overlay. Hetk gives you true two-way sync with the real-time updates that manual subscriptions can’t match.

Related

• How to subscribe to ICS in Google Calendar
• How to sync iCloud with Outlook
• Hetk vs Zapier for calendar sync