Duplicate Detection

Ever downloaded the same video twice by accident? Maybe you forgot you already had it, or you're re-downloading a playlist that's mostly videos you already saved. Fetchii's duplicate detection prevents this by remembering every video you've downloaded and warning you before downloading it again.

How It Works

Every video has a unique identifier — a string of characters that identifies exactly that video on that platform. When you download a video, Fetchii records this ID in its downloaded records. The next time you try to download the same video, Fetchii checks the records, finds the match, and lets you know.

The records are a simple text file that Fetchii manages automatically. Each line records a platform and video ID, like youtube dQw4w9WgXcQ or vimeo 123456789. When you've downloaded thousands of videos over the years, these records become invaluable for avoiding redundant downloads.

Enabling Duplicate Detection

Duplicate detection is on by default. You'll find it in Fetchii → Settings → Downloads → Duplicate Detection: Enable duplicate detection turns it on or off, and the Downloaded records row shows how many videos Fetchii remembers.

Videos you download while it's off aren't remembered.

When you add a video that's already in your records, Fetchii shows a Previously Downloaded sheet. Click Download Anyway to get another copy, or Cancel to skip it. If the video is still in your download list, you'll see Already Downloaded instead, with Show in Finder and Download Again.

Handling Playlists

Duplicate detection really shines with playlists. Say you're following a YouTube series that adds new episodes weekly. Every week, you can just paste the playlist URL. In the playlist sheet, videos you already have are marked, and with Auto-exclude downloaded ticked they start out unselected — so only the new episodes are downloaded.

If a playlist has videos you already downloaded, the sheet also shows a filter — All, New and Downloaded, with counts — so you can review what you have. Already-downloaded videos stay in the list, and you can tick any of them to download it again.

When You Want to Re-Download

Sometimes you legitimately want to download something again — maybe you deleted the original file, or you want a different quality. There are a few ways to handle this:

Download anyway: When Fetchii shows the duplicate warning, click Download Anyway (or Download Again for a video still in your list).

Remove the record: Go to Downloaded records, click Manage… and choose View Records…. Search for the platform or video ID, select the entry and click Delete Selected. Now Fetchii doesn't know you downloaded it before.

Move to Trash: When you remove a finished download with Move to Trash…, Fetchii forgets its record too. Remove from List keeps the record, so you're still warned later.

Quality and Duplicates

Duplicate detection doesn't consider quality. If you downloaded a video in 1080p and later want the 4K version, Fetchii still flags it as a duplicate because it's the same video. Click Download Anyway to get the other quality.

Managing Your Records

Over time, your records grow to include every video you've ever downloaded. Everything is in the Manage… menu next to Downloaded records:

Viewing the Records

Choose View Records… to open the Download Archive window. Entries are grouped by platform, and you can search by platform or video ID, copy an ID, or delete selected entries.

Backing Up

Before major system changes, choose Export… and save the file somewhere safe. This file represents your entire download history for duplicate detection purposes.

Restoring from Backup

If you need to restore, choose Import… and select your backup file. The entries merge with your current records; entries you already have are skipped, and Fetchii tells you how many were imported.

Moving to a New Mac

When migrating to a new computer, export your records on the old Mac and import them on the new one. Your duplicate detection history transfers seamlessly — Fetchii on your new Mac knows about everything you downloaded on the old one.

Starting Fresh

If you want to clear all duplicate detection history, choose Clear All Records… and confirm. Fetchii will treat all videos as new downloads; your files aren't affected. Only do this if you're sure — export a backup first, because there's no undo.

Note that Clear Download History (under Settings → Downloads → Storage) is something else: it removes finished and failed entries from the download list and leaves your records alone.

Troubleshooting

False positives (says duplicate but isn't): This is rare, but can happen if two different videos somehow share an ID. Remove the entry in View Records… and try again. You can also just click Download Anyway on the duplicate warning.

Not detecting duplicates: Make sure Enable duplicate detection is on, and check that Downloaded records shows a count rather than "No records yet". Videos downloaded while detection was off aren't recorded. If a video was re-uploaded (deleted and uploaded again by the creator), it has a new ID and won't be detected as a duplicate.

Records seem corrupted: If you're seeing strange behavior, choose Remove Invalid Records in the Manage… menu. This scans the records for malformed entries and removes them. If problems persist, you can export (as backup), clear, and start fresh.

Practical Tips

Keep it enabled. There's almost no downside to duplicate detection, and it saves bandwidth and disk space over time. Leave it on as your default.

Regular backups. If your records represent years of downloads, export them occasionally. Include the file in your general Mac backup routine.

Don't worry about size. Even with tens of thousands of entries, the file stays small (a few megabytes at most) and checking against it is instantaneous.

For shared computers. Each macOS user account has its own records. If several people share one account, they share the records too, which might lead to unexpected duplicate warnings.