elasticsearch/docs/reference/mapping/fields/source-field.asciidoc

[[mapping-source-field]]
=== `_source`

The `_source` field is an automatically generated field that stores the
actual JSON that was used as the indexed document. It is not indexed
(searchable), just stored. When executing "fetch" requests, like
<<docs-get,get>> or
<<search-search,search>>, the `_source` field is
returned by default.

Though very handy to have around, the source field does incur storage
overhead within the index. For this reason, it can be disabled. For
example:

[source,js]
--------------------------------------------------
{
    "tweet" : {
        "_source" : {"enabled" : false}
    }
}
--------------------------------------------------