Calendar invitations

See what is in a calendar invitation without adding it

You can read an .ics invitation without letting it into your calendar. An .ics is a plain text file listing the event's title, times, location, organiser and guests, so it can simply be read. Foretaste reads it from the link and shows you those fields; nothing is added to any calendar, because nothing hands the file to a calendar application.

An .ics lands in your downloads, and every offer your machine makes is the same offer: open it, and let a calendar application put it in your diary. You wanted to know who the meeting is with and what time it is for you — not to acquire it.

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An .ics is a text file, which helps

There is no mystery in the format, and knowing that changes what you can do with it. An .ics is lines of NAME:value, grouped into blocks that begin and end by name — the iCalendar format, RFC 5545. One event is a VEVENT block holding SUMMARY, DTSTART, DTEND, LOCATION, ORGANIZER and so on. A file can hold several.

It is the same shape as a .vcf contact card, down to the way both wrap long lines and escape commas, which is why one reader handles both.

The consequence: an .ics can be read. Nothing about the format requires it to go into a calendar to be understood. That is a habit of the applications registered to open it, not a property of the file.

Why opening one feels like a commitment

Because on most machines it is. Double-clicking an .ics hands it to whichever application claimed the file type, and that application's first instinct is to offer to add the event — sometimes as a dialog you dismiss, sometimes as a tentative entry that is already in the diary while you decide.

In the browser it is worse in a smaller way: an invitation behind a link is usually served as an attachment, so the only thing offered is a download. Why a link downloads instead of opening is the general version of that, and it is the same header at work.

So the question people actually have — what is this, before I accept it — is the one thing neither route answers.

What Foretaste shows

Right-click the link and choose Open with Foretaste, and you get every event in the file, read in your own browser. For each one, in the order you would read them: what it is, when it starts and ends, where, who organised it, who else was asked, whether it repeats, its status, any link on it, and its description.

The times are the part worth explaining, because they are where a reader is most easily misled and the format offers three different shapes:

A time in UTC is converted and shown in your own locale, which is the question you were actually asking.
A time with a named zone is shown with that zone printed beside it, rather than silently converted.
A time with no zone at all is labelled as having none. The format permits this, and presenting a guess as a fact is how an invitation ends up an hour out.
An all-day date is never shifted into a time zone. That shift is how a birthday lands on the wrong day.

Above the list, the file's own facts: how many events it holds, and how many blocks parsed to nothing — counted rather than quietly dropped, because a file that half-parsed is worth knowing about.

A .vcf contact card goes through the same reader and shows the fields a card carries instead. Both are on the format list.

What it is not, and where a calendar is better

This is a reader, not a calendar, and for several real jobs a dedicated viewer is the better answer.

A repeating event shows its rule, not its dates. You see that it repeats and by what rule; you do not get a generated list of occurrences, or a month view, or exceptions applied. Dedicated .ics viewers do all three and are the right tool when that is the job.
Events and tasks only. VEVENT and VTODO blocks are read. Other block types a file may carry are not shown.
An attached file inside the invitation is not read. The properties listed above are what is shown.
Nothing is added anywhere. Foretaste has no access to any calendar, on your machine or elsewhere, so there is no import, no tentative entry, and nothing to undo. Reading is all it does.
It does not tell you whether an invitation is genuine. It shows you the fields the file contains. Whether the organiser is who they say they are is not something the file can settle and not something Foretaste judges.

The file is read on your own machine and goes nowhere — the whole of what Foretaste can and cannot see is written down, and an invitation full of names is a reasonable example of why that matters.

The questions people ask

Can I open an .ics file without adding it to my calendar?

Yes, if something reads the file rather than handing it to a calendar application. An .ics is plain text, so the contents can be shown directly. Foretaste reads it in the browser tab and lists the events in it; nothing is written to any calendar, because Foretaste has no access to one.

What does an .ics file actually contain?

Lines of NAME:value grouped into BEGIN and END blocks, defined by RFC 5545. An event is a VEVENT block holding properties such as SUMMARY, DTSTART, DTEND, LOCATION, ORGANIZER and ATTENDEE. It is the same shape as a .vcf contact card, which is why one parser reads both.

What does Foretaste show for a calendar invitation?

Every event in the file, with what it is, when it starts and ends in your own locale, where it is, who organised it, who else was asked, whether it repeats, its status, any link and its description. It also says how many events the file holds, and counts any blocks that parsed to nothing rather than hiding them.

Does it expand a repeating event into dates?

No. A repeating event shows the recurrence rule it repeats by, not a generated list of occurrences. Dedicated calendar viewers do expand that rule, and if working through the individual dates is what you need, one of those is the better tool.