iCalendar Validator
Validate ICS files against RFC 5545. Check syntax errors, missing properties, and fix calendar file issues instantly.
📁 Drag and drop your ICS file here
or
Why Use Our iCalendar Validator?
🔒 100% Private & Secure
All validation happens client-side in your browser. Your ICS file content never leaves your device, ensuring complete privacy and security.
✅ RFC 5545 Compliant
Validates against the official RFC 5545 specification, ensuring your calendar files work correctly across all calendar applications.
📋 Detailed Error Reports
Get precise error messages with line numbers, property names, and helpful suggestions to fix issues quickly.
🚀 Multiple Input Methods
Validate files by uploading, pasting content, or fetching from a URL. Works with files up to 10MB in size.
What Does the iCalendar Validator Check?
File Structure
- Proper BEGIN:VCALENDAR and END:VCALENDAR tags
- Matching BEGIN/END tag pairs
- Correct component nesting (VEVENT, VTODO, VJOURNAL)
- CRLF line endings (RFC 5545 requirement)
Required Properties
- VERSION property (must be 2.0)
- UID (unique identifier) for each event
- DTSTAMP (timestamp)
- DTSTART (start date/time)
- DTEND or DURATION for events
Data Validation
- Valid date-time formats (ISO 8601)
- DTEND must be after DTSTART
- Duplicate UID detection
- RRULE recurrence rule syntax
- Timezone format validation
Common Use Cases for iCalendar Validation
Our iCalendar validator helps developers, calendar administrators, and users ensure their ICS files are properly formatted and compatible across different calendar applications. Here are some common scenarios:
- Calendar Integration: Validate ICS files before importing into Google Calendar, Outlook, Apple Calendar, or other calendar applications
- API Development: Test and debug calendar feeds for web applications and APIs that generate ICS files
- Event Management: Ensure event files exported from event management systems are RFC 5545 compliant
- Calendar Sync: Fix calendar synchronization issues by identifying and correcting invalid calendar file formats
- Quality Assurance: Validate calendar files before distribution to ensure they work correctly for all recipients
Common ICS File Errors & How to Fix Them
Missing Required Properties
Error: Missing UID, DTSTAMP, or DTSTART properties
Fix: Every VEVENT must have a unique UID, a DTSTAMP (timestamp of creation), and a DTSTART (start date/time). Add these properties to each event in your ICS file.
Invalid Date-Time Format
Error: Date-time values not in correct format
Fix: Use ISO 8601 format: YYYYMMDDTHHMMSSZ for UTC times or YYYYMMDDTHHMMSS for local times. Example: 20250101T120000Z for January 1, 2025 at 12:00 PM UTC.
DTEND Before DTSTART
Error: DTEND date-time is before DTSTART
Fix: Ensure DTEND occurs after DTSTART. For all-day events, use DATE format (YYYYMMDD) and make sure the end date is after the start date.
Duplicate UIDs
Error: Multiple events with the same UID
Fix: Each event must have a unique UID. Generate unique identifiers using UUIDs or a combination of timestamp and random characters.
Mismatched BEGIN/END Tags
Error: BEGIN:VEVENT without matching END:VEVENT
Fix: Ensure every BEGIN tag has a corresponding END tag with the same component name. Check for typos and missing closing tags.