About the ICS Editor

The ICS Editor is a free tool by Thomas Freimoser from Munich, Germany. It exists because large or non-English calendar files keep failing to import into Google Calendar – and because practices, clubs and small businesses need to split shared calendars when moving to individual accounts.

What the tool does – and what it doesn’t

The ICS Editor reads ICS files, Google Calendar’s ZIP export and CSV or Excel spreadsheets, shows every calendar and event, lets you edit, filter and split them and writes files that Google Calendar accepts. It does not edit your Google Calendar directly: it never connects to your Google account. You import the files yourself, on a computer.

How it’s tested

  • Automated tests with generated sample data: semicolon CSV in Windows encoding, Excel with date values, a 3 MB event list, broken rows, ambiguous dates, birthdays on 29 February.
  • Every generated ICS file is checked with an independent iCalendar reader (ical.js), every Google CSV against the format in Google’s help.
  • Browser tests check use on phones (360 px), by keyboard, offline – and that processing a file causes no network request at all.
  • In addition, a real Google Calendar export of a veterinary practice with about 27,000 events went through the tool – analysed only locally, without names. Its key figures appear in the guides as a real-world example. In addition, an exported part with 999 events was imported into Google Calendar on a computer: Google reported 999 of 999 events imported (October 2026, see import a calendar in parts).

Where the facts come from

Every statement about Google Calendar – such as the 1 MB limit per file – comes from Google’s official help and is linked with a date on each page. Own measurements are marked as such. The source code is public: github.com/freimoser/ics-editor.

Your data

Your files never leave your device. There is no server that accepts files, no tracking and no cookies. Details are in the privacy policy.

Contact

Found a bug or have an idea? Write to 91Serdar [at] gmail.com or via LinkedIn. More in the legal notice.