OBJECT ENCODING key

Returns the internal encoding for the Redis object stored at <key>

Redis objects can be encoded in different ways:

• Strings can be encoded as raw (normal string encoding) or int (strings representing integers in a 64 bit signed interval are encoded in this way in order to save space).
• Lists can be encoded as ziplist or linkedlist. The ziplist is the special representation that is used to save space for small lists.
• Sets can be encoded as intset or hashtable. The intset is a special encoding used for small sets composed solely of integers.
• Hashes can be encoded as ziplist or hashtable. The ziplist is a special encoding used for small hashes.
• Sorted Sets can be encoded as ziplist or skiplist format. As for the List type small sorted sets can be specially encoded using ziplist, while the skiplist encoding is the one that works with sorted sets of any size.

All the specially encoded types are automatically converted to the general type once you perform an operation that makes it impossible for Redis to retain the space saving encoding.

Return

Bulk string reply: the encoding of the object, or nil if the key doesn't exist