.ics / iCal File Validator

ICS / iCal File Validator - Check Calendar Files Online

How do I validate an ICS file?

Upload your .ics or iCal file to this validator and it will instantly parse the contents, check for structural errors, and confirm whether the file conforms to the iCalendar format. The tool reports the number of events found along with each event's title and date, giving you a quick overview without needing to import the file into a calendar application first.

What does this iCal validator check for?

The validator parses your file against the iCalendar specification (RFC 5545). It checks that the file structure is well-formed, that required components like VCALENDAR and VEVENT are present and correctly nested, and that date-time values and properties use valid syntax. If any parsing error is encountered, the tool displays the specific error message so you can locate and fix the issue.

Can I validate an ICS file without uploading it to a server?

Yes. This tool runs entirely in your browser. Your calendar file is never sent to any external server or stored anywhere outside your device. The validation and parsing happen locally using JavaScript, making it safe to check files that contain private event details, attendee information, or other sensitive calendar data.

What is the difference between ICS and iCal files?

ICS (iCalendar) files and iCal files refer to the same format defined by RFC 5545. The .ics extension is the standard file extension for iCalendar data. Whether your file comes from Google Calendar, Apple Calendar, Outlook, or any other calendar application, this validator handles them all identically since they share the same underlying format.

How do I fix an invalid ICS file?

When the validator reports an error, the error message typically points to the exact parsing issue - such as malformed date values, missing required properties, or broken line folding. You can open the file in a text editor to correct the issue and re-upload it. For files exported from calendar applications, re-exporting from the source application often resolves formatting problems. You can also use our iCal Event File Creator to generate correctly formatted ICS files from scratch.

Can I view the full details of events after validation?

After validating your file, use the "View Full Event Contents" button to open the file in our ICS File Viewer, which displays complete event details including descriptions, attendees, recurrence rules, reminders, and organizer information. The file content is passed directly between tools without re-uploading.

Does this tool support ICS files with multiple events?

Yes. The validator handles ICS files containing any number of events. After parsing, it reports the total event count and lists each event with its title and start date. This is useful for verifying calendar exports, bulk event files, or merged calendars before importing them. You can also use our ICS File Combiner to merge multiple calendar files into one.

Can I validate ICS files with recurring events?

The validator correctly parses files that contain recurring events with RRULE properties. It will report each event entry found in the file. To inspect the full recurrence rule details, use the "View Full Event Contents" button to open the file in the ICS File Viewer, which renders recurrence patterns in a human-readable format.

What calendar applications export ICS files I can validate?

Any standards-compliant calendar application exports ICS files that this tool can validate. This includes Google Calendar, Apple Calendar (iCal), Microsoft Outlook, Thunderbird, Fastmail, Proton Calendar, and many others. The tool is also useful for developers building calendar integrations who need to verify that their generated ICS output is syntactically correct.