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Merge and Deduplicate Calendars

Combine supported ICS event files and resolve duplicate event identifiers using an explicit policy.

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How this works

The tool runs in this browser. Your file or text is not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

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Drop your files here

or choose them from your device

Choose 2–8 UTF-8 ICS files; at most 5 MiB combined and 200 events before deduplication. UTC or all-day events with explicit ends only. File order controls which duplicate UID survives.

    UID identity only. Equal-looking events with different UIDs remain separate; sequence numbers and dates do not select a revision.

    How to use Merge and Deduplicate Calendars

    1. Choose the ICS files in the intended order.
    2. Choose how duplicate event identifiers should be handled.
    3. Review the report and import the merged download into a test calendar.

    Example: Merge and Deduplicate Calendars

    A local worked example using the inputs and settings below for merge and deduplicate calendars.

    You add
    Calendar files in merge order: ["first.ics (209 bytes)","second.ics (208 bytes)"] Repeated UID policy: "refuse"
    You get
    Merged 2 files: 2 input events, 2 kept and 0 discarded duplicate UIDs. first | Planning | 20260105T090000Z | 20260105T100000Z second | Review | 20260105T090000Z | 20260105T100000Z merged-calendar.ics deduplication-report.csv

    Options

    File order
    Choose two to eight files in the intended order. First or last occurrence uses that order, not event modification dates or sequence numbers.
    Repeated UID policy
    Refuse identifies duplicate identities for review. Keep first or keep last drops the other entries with that same UID; different UIDs remain separate.

    Supported inputs and limits

    Two to eight files, 20 MiB total and 200 events before deduplication. Finite VEVENT entries with explicit end, UTC times or all-day dates only. Recurrence, invitations, named time zones, alarms, attachments and calendar methods are refused. Duplicate UIDs use refusal, first-file or last-file policy. Dates use years 1970–2100; UTC timestamps require explicit seconds. Unsupported properties and parameters are refused.

    Where your input is processed

    This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

    Equal titles do not establish duplicate events

    The tool deduplicates UID identity only. Two events that look alike can have different identities, and two versions of one UID can contain important differences. Review the discard report before importing the merged calendar.

    Questions about Merge and Deduplicate Calendars

    Are events compared by their titles?

    No. Deduplication uses event identifiers. Similar titles with different UIDs remain separate.

    Can recurring calendars be merged?

    No. Recurring events and time-zone definitions are outside the supported subset.

    Does selecting last keep the newest edit?

    It keeps the last input occurrence, without comparing edit timestamps. Order the files carefully.

    Project manager: Tony Hines · Content updated 4 October 2026 · Report a problem

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