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ICS converter

A .ics file is an iCalendar document: a text container of events, to-dos, journal entries and free/busy blocks, written as folded property lines inside BEGIN/END component blocks. It is what every calendar invitation you have ever received is made of.

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Drop ICS files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where ICS comes from

RFC 2445 defined iCalendar in 1998, building on the earlier vCalendar work from the Versit consortium, and RFC 5545 replaced it in 2009. It became universal because it solved interoperability between Outlook, Lotus Notes and everything that followed — an emailed .ics attachment is still the only calendar invitation format that every client understands.

How ICS works

  • Components nest: VCALENDAR contains VEVENT, VTODO, VJOURNAL, VFREEBUSY and VTIMEZONE blocks.
  • Lines are folded at 75 octets with a leading space on continuations, so naive line-based parsing corrupts long values.
  • Recurrence is expressed by RRULE, an expression language capable of rules most calendar UIs cannot display.
  • Timezones are carried as VTIMEZONE definitions inside the file rather than by reference, so a file is self-contained.
  • UIDs identify events across updates, which is how a rescheduled meeting replaces rather than duplicates the original.

When to use ICS

  • Sending and accepting meeting invitations between different calendar systems
  • Publishing a subscribable schedule for a team, venue or sports season
  • Exporting a calendar for backup or migration
  • Extracting events into a spreadsheet for reporting

Strengths and limitations

Strengths

  • Universally supported — the one calendar format everything reads
  • Self-contained timezone definitions avoid depending on the reader's database
  • Expressive recurrence rules cover genuinely complicated schedules

Limitations

  • Line folding makes the format deceptively hard to parse correctly
  • RRULE is powerful enough that clients disagree on edge cases
  • Verbose relative to the information it carries

Compatibility

Read by Google Calendar, Outlook, Apple Calendar, Thunderbird and effectively every scheduling tool. Novus Convert parses events locally and converts to JSON and CSV, unfolding continuation lines first so long descriptions and locations survive intact.

Event fields — UID, summary, start, end, location and description — are preserved. Recurrence rules and embedded timezone definitions are not expanded into flat tabular output.

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