ICS Calendar Subscription Not Working – Has the Feature Been Paused?

TD 160

Hello,

I’ve noticed that the ICS calendar subscription feature is not working anymore. Subscribing to external calendars via an ICS link used to work reliably, but recently it isn't possible to subscribe to calendars anymore. In my office we are all unable to do it so it isn't just me.

Is this a temporary issue or a known bug?

ICS subscription is an essential feature for me, so I’d greatly appreciate an update on its current status.

Thank you! Screenshot 2025-08-20 at 10.52.47

JB 25 Reputation points

2025-08-21T14:13:51.9+00:00

Just within the past week I, too, noticed that subscribing to my Outlook calendar with an external calendar via an .ics link was no longer updating. When I deleted and re-added the subscription, no events from my Outlook calendar were retrieved. This feature did work for years. The .html link for publishing a calendar does still work, however.
Anonymous

2025-08-21T23:00:13.0333333+00:00

This is exactly my situation too ☹️
Amanda 5 Reputation points

2025-08-25T22:07:31.2966667+00:00

I have the same issue. Need the ics to subscribe to calendar on macOS/ iOS

Anomalie Malz 10

I have the same problem. When I try to publish my work calendar the HTML URL works, but the ICS URL responds with:

<html><head><title>Object moved</title></head><body><h2>Object moved to <a href="/owa/auth/errorfe.aspx?httpCode=500&amp;msg=3673577647&amp;owaError=Microsoft.Exchange.Clients.Owa2.Server.Core.OwaBasicUnsupportedException&amp;owaVer=15.20.9073.21&amp;be=redacted&amp;ts=134013641080231510&amp;fe=redacted&amp;reqid=&amp;creqid=&amp;cid=&amp;hmac=redacted.">here</a>.</h2></body></html>

Mansoor Lunawadi 0 Reputation points

2025-09-06T01:41:04.0266667+00:00

Another way to do it is to get the link to the HTML calendar. Look in the Network tab for a request which gives the events. I believe it is

service.svc?action=FindItem&app=PublishedCalendar&n=2

The response of this request gives a big JSON with all the events of the calendar.

Can use Selenium and requests library in python to automate.
J. Raff 0 Reputation points

2025-09-09T14:48:33.7766667+00:00

Same problem since end of August 2025 here! Any kind of import of .ics or .html URL from outlook into my personal Google calendar fails (with some notable exceptions: when events are added by a third party to my outlook calendar). Greetings from Berlin, Germany.
Anand Patil 0 Reputation points

2025-09-10T15:40:53.46+00:00

Can confirm this has broken my sync between exchange and google calendars. This is used for a pretty major function within my org, and I'm not sure what to do in the interim.
Anand Patil 0 Reputation points

2025-09-10T15:41:37.6466667+00:00

Can confirm this has broken my sync between exchange and google calendars. This is used for a pretty major function within my org, and I'm not sure what to do in the interim.
Jennifer 0 Reputation points

2025-09-12T18:16:27.58+00:00

Same issue. Last sync was August 20, 2025.
Michael Spaeth 0 Reputation points

2025-09-17T13:20:18.5633333+00:00

I have the opposite problem at the moment - subscribing to my Outlook calendar via the published ICS for use in an external planning tool has stopped working. Anyone else out there experiencing the same problem?

I can download the ICS file, so it's definitely there, and curl also provides a positive response, but the external tool fails with a HTTP 302 error message.
Jeff Lawrence 25 Reputation points

2025-09-17T19:00:58.9466667+00:00
@Michael Spaeth Sounds like the same problem if I understand your post, whatever external planning tool you are using is most likely using a browser user agent that Microsoft blocks, while you testing in a browser using an approved user agent works (which is the reported behavior). When you use curl are you passing a user agent?

13 answers

Leon 45 Reputation points

2025-08-21T18:47:31.7033333+00:00

it seems that the ics link only works in a Browser with a Browser User-Agent (at least with Firefox ics download works). All other User Agents seem to be redirected to an error 500 page. Therefore Apps are not able to sync the ics anymore. (curl fails with default User Agent and succeeds with one from Firefox)
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kb-8356 15 Reputation points

2025-09-02T10:08:29.1766667+00:00

I can't believe that Microsoft just breaks a feature by prohibiting other user-agents without notifying paying customers...
This means that every third-party calendar subscription app, e.g. Apple calendar, is broken for more than two weeks now @Winnie-B .
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Jan Dzieciol 120 Reputation points

2025-09-20T19:52:00.7033333+00:00

Hello everyone, I've developed a small web app to serve as a workaround until Microsoft releases a fix for the issue. Please note that it's still a work in progress, so use it with caution: https://calconverter.app/

Raphael's self-hosted PHP file is probably much more reliable and secure but for anyone who isn't able to set up a server the web app might be useful until Microsoft fixes the problem.
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Amanda 5 Reputation points

2025-09-21T01:13:09.44+00:00

THANK YOU SO MUCH!

Anonymous

2025-09-22T09:03:36.06+00:00

It worked, thanks!

P.D: GitHub link doesn't works, I wanted to give a star :-)

Steffen Luf 0 Reputation points

2025-09-24T11:35:59.8333333+00:00

Thank you very much!
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A B 25 Reputation points

2025-09-03T09:46:17.4766667+00:00

It works when faking the user agent.

With default curl user agent it does not work:

With fake user agent it works:

#enshittification
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Anomalie Malz 10 Reputation points

2025-09-03T12:05:58.3933333+00:00

Nice finding. Doesn't help me unfortunately, because I need to add the link as a subscription to the macOS and iOS Calendar.

kb-8356 15 Reputation points

2025-09-03T16:18:35.1966667+00:00

Same here...can't fake it. MS needs to fix it.

Bogdan Pavel 15 Reputation points

2025-09-03T19:09:26.8233333+00:00

We have been investigating this issue and confirmed that it’s not isolated to our tenant. The problem with Office 365/Exchange Online shared calendar subscription links (.ics) is also being discussed in other forums. For example, Thunderbird users are reporting the exact same behavior where the calendar link redirects return errors (eg OwaBasicUnsupportedException) unless a user agent workaround is applied.

https://bugzilla.mozilla.org/show_bug.cgi?id=1984590

https://github.com/bitfireAT/icsx5/discussions/654

This suggests the issue is more widespread, and may be related to how certain clients (Thunderbird, Apple Calendar, etc.) handle redirects from Exchange Online calendar publishing URLs. In browsers, the .ics downloads correctly, but in calendar clients the subscription fails

A B 25 Reputation points

2025-09-11T08:17:39.1966667+00:00

It is not related to redirects. As I wrote in my post above it is the difference in user-agents. Browser user-agents in HTTP requests work fine and all other clients with their own user-agent string are excluded. I am resorting to use vdirsyncer now which allows setting custom user-agent strings.
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Raphael 20 Reputation points

2025-09-19T17:41:15.1066667+00:00

I initially thought it was just a temporary problem. Thanks to this thread, I then knew the cause and created a minimal script that can run on any server with PHP support and more or less just changes the User-Agent while passing along the ICS URL. Any error messages are rudimentarily displayed as events.

The usage is https://example.tld/some/path/ics-proxy.php?url=<your outlook calendar url>

In my case, I use it in Google Calendar and it works - but it should work in almost any app that uses .ics-URLs I guess. Hopefully this helps someone here, too :)

https://github.com/RaphaelBergmann/ICS-Proxy
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Juan Cabrera Jamoulle 40 Reputation points

2025-09-24T16:20:17.05+00:00

Thank you for this PHP script. The ics links no longer work with Calendar (in Mac OS) or with Thunderbird. This solution works very well. But this problem must be temporary. Microsoft must fix the issue.

Jennifer 0 Reputation points

2025-09-29T23:07:59.4633333+00:00

Thank you for this script. Works like a charm!
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Jeff Lawrence 25 Reputation points

2025-09-04T23:16:50.1633333+00:00

Having same issue, broken calendar display recently from both Magic Mirror and Home Assistant. The fix to change useragent string fixes it as mentioned earlier.

Unfortunately this isn't an option for everything, Microsoft can you please fix this?
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ICS Calendar Subscription Not Working – Has the Feature Been Paused?

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