Question 1

How do I validate an ICS file?

Accepted Answer

Click "Open .ics file" above and choose your file, or paste its contents into the box. It is checked straight away: any errors appear under the box, and every event the validator can read is listed below them.

Question 2

What does the validator check?

Accepted Answer

That the calendar has PRODID and VERSION and contains at least one event, task or journal entry. For each event, that UID, DTSTAMP and DTSTART are present, dates and times are written correctly, the end isn’t before the start, and any repeat rule (RRULE) is valid. It also flags time zones that are used without a VTIMEZONE definition.

Question 3

Is this an iCal validator too?

Accepted Answer

Yes. iCal and ICS are the same format, iCalendar, so this checks .ics, .ical and .icalendar files. It also works on calendar text pasted straight from ChatGPT, Gemini or another app.

Question 4

What is the difference between an error and a warning?

Accepted Answer

An error means the file breaks a rule, and a calendar app may refuse it or lose events. A warning is only worth a look, such as an event that has already happened; the file is still valid.

Question 5

How do I fix the errors it finds?

Accepted Answer

Click Fix. It repairs the common problems: missing VCALENDAR wrappers, missing VERSION, PRODID, UID or DTSTAMP, badly written dates, end dates before start dates, and stray text around the calendar data. If a file is too damaged for that, Fix with AI can try to rebuild it.

Question 6

My file passes, but my calendar app still rejects it. Why?

Accepted Answer

A pass means the file follows the rules listed above, not that every app will take it. Calendar apps add limits of their own, such as a maximum file size, so check the app’s own import error message as well.

Question 7

Is my file uploaded anywhere?

Accepted Answer

No. Opening, checking and the standard Fix all happen in your browser. Only Fix with AI sends the file to our server, because that is where the repair runs.

Question 8

Is it free?

Accepted Answer

Opening, checking and repairing your file is free. Downloading it (as .ics, PDF or a spreadsheet) is a one-time payment: $2 for this file, or $5 for every file, forever.

ICS Validator — Check a Calendar File for Errors

Frequently Asked Questions