 <p>In the shell, use db.collection.stats(). If a collection is capped:</p> <pre><code>&gt; db.my_collection.stats()["capped"] 1 </code></pre> <p>If a collection is not capped, the "capped" key will not be present.</p> <p>Below are example results from stats() for a capped collection:</p> <pre><code>&gt; db.my_coll.stats() { "ns" : "my_db.my_coll", "count" : 221, "size" : 318556, "avgObjSize" : 1441.4298642533936, "storageSize" : 1000192, "numExtents" : 1, "nindexes" : 0, "lastExtentSize" : 1000192, "paddingFactor" : 1, "flags" : 0, "totalIndexSize" : 0, "indexSizes" : { }, "capped" : 1, "max" : 2147483647, "ok" : 1 } </code></pre> <p>This is with MongoDB 1.7.4.</p>