What are duplicate filters?

A duplicate filter hides an article when an earlier article in the same feed, folder, monitoring feed or Newsfeed has the same URL, the same title or a nearly identical title, so a story carried by several sources appears once. The first copy stays, and the later ones are marked read and hidden.

Choose how duplicates are matched

Under Filter duplicate articles when they have, pick the same URL (the default and the safest choice), the same title or nearly identical titles. The Comparison period slider sets how far back Inoreader compares, from 6 hours to 1 month, with 1 day as the default. For nearly identical titles, Filter precision offers loose, moderate and strict. A loose filter needs fewer words to match. How are duplicate articles detected? explains each method.

Set one up

1. Right-click a feed or folder and choose Filter feed or Filter folder, or go to Automate > Filters, click Create filter and pick the source.
2. Click Remove duplicates.
3. Under Filter duplicate articles when they have, choose the same URL, the same title or nearly identical titles.
4. Set the Comparison period, and for nearly identical titles the Filter precision.
5. Click Save filter.

The Automations tab of Feed properties or Folder properties sets the same filter up with the switch Remove duplicate articles from this feed or Remove duplicate articles from this folder, a method menu and Advanced options for the period and precision. The Newsfeed's Feed properties has Remove duplicate articles for everything you follow.

Inoreader recommends duplicate filters on the folders and feeds known to produce duplicates rather than on your whole account.

After saving

The filter also runs over the recent articles of its sources within the comparison period, and the notice "Deduplication filter created." reports how many similar articles it filtered, with View filter log. The filter log lists each Original article with its Filtered duplicates, and the Removed today count in Automate > Filters opens it later. A duplicate filter on the Newsfeed pauses your other duplicate filters that use the same method until you turn it off. Turning a filter off or deleting it brings the hidden copies back as unread.

Filters are a Pro feature: duplicate filters count toward the same 50 as content filters, and How many filters are included in Pro plans? covers the limit. What are filters? explains the other kind, the content filter.