What does an ICS validator do?

An ICS validator checks iCalendar (.ics) structure, required properties (like DTSTART/UID/VERSION), timezone correctness (TZID/VTIMEZONE), and formatting issues that cause imports to fail.

Is “validate ICS” the same as “ICS validator”?

Yes. “Validate ICS” usually means running the file through an ICS validator to find errors and warnings before importing into Google Calendar, Outlook, or Apple Calendar.

Why should I fix the first error first?

Many calendar clients stop parsing after the first critical error. Fixing the earliest error often makes later errors disappear.

ICS Validator: how to validate an ICS file (and fix it)

If you searched for “ICS validator” or “validate ICS”, you’re usually trying to do one of these:

figure out why an .ics file won’t import into Google Calendar / Outlook / Apple Calendar
fix “invalid iCalendar / invalid ICS file” errors
stop events from showing at the wrong time (TZID/VTIMEZONE issues)

Use the free ICS validator to understand what’s wrong, then upload the file to /fix to download a repaired .ics when fixes are available.

What an ICS validator checks (in plain language)

An ICS validator typically checks:

Structure: BEGIN:VCALENDAR…END:VCALENDAR, and BEGIN:VEVENT…END:VEVENT
Required fields: DTSTART, UID, VERSION, PRODID (and more, depending on the client)
Time zones: valid TZID values and whether a matching VTIMEZONE is present when needed
Formatting: line folding, invalid characters, broken encodings