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+# Redundancy
+
+A PeerTube instance can cache other PeerTube videos to improve bandwidth of popular videos or small instances.
+
+## How it works
+
+The instance administrator can choose between multiple redundancy strategies (cache trending videos or recently uploaded videos etc), set their maximum size and the minimum duplication lifetime.
+Then, they choose the instances they want to cache in `Manage follows -> Following` admin table.
+
+Videos are kept in the cache for at least `min_lifetime`, and then evicted when the cache is full.
+
+When PeerTube chooses a video to duplicate, it imports all the resolution files (to avoid consistency issues) using their magnet URI and put them in the `storage.videos` directory.
+Then it sends a `Create -> CacheFile` ActivityPub message to other federated instances. This new instance is injected as [WebSeed](https://github.com/Chocobozzz/PeerTube/blob/develop/FAQ.md#what-is-webseed) in the magnet URI by instances that received this ActivityPub message.
+
+## Stats
+ 
+See the `/api/v1/server/stats` endpoint. For example:
+
+```
+{
+  ...
+  "videosRedundancy": [
+    {
+      "totalUsed": 0,
+      "totalVideos": 0,
+      "totalVideoFiles": 0,
+      "strategy": "most-views",
+      "totalSize": 104857600
+    },
+    {
+      "totalUsed": 0,
+      "totalVideos": 0,
+      "totalVideoFiles": 0,
+      "strategy": "trending",
+      "totalSize": 104857600
+    },
+    {
+      "totalUsed": 0,
+      "totalVideos": 0,
+      "totalVideoFiles": 0,
+      "strategy": "recently-added",
+      "totalSize": 104857600
+    }
+  ]
+}
+```
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