[[mapping-boost]]
=== `boost`

Individual fields can be _boosted_ automatically -- count more towards the relevance score
-- at query time, with the `boost` parameter as follows:

[source,console]
--------------------------------------------------
PUT my-index-000001
{
  "mappings": {
    "properties": {
      "title": {
        "type": "text",
        "boost": 2 <1>
      },
      "content": {
        "type": "text"
      }
    }
  }
}
--------------------------------------------------
// TEST[warning:Parameter [boost] on field [title] is deprecated and will be removed in 8.0]

<1> Matches on the `title` field will have twice the weight as those on the
    `content` field, which has the default `boost` of `1.0`.

NOTE: The boost is applied only for term queries (prefix, range and fuzzy queries are not _boosted_).

You can achieve the same effect by using the boost parameter directly in the query, for instance the following query (with field time boost):

[source,console]
--------------------------------------------------
POST _search
{
  "query": {
    "match": {
      "title": {
        "query": "quick brown fox"
      }
    }
  }
}
--------------------------------------------------

is equivalent to:

[source,console]
--------------------------------------------------
POST _search
{
  "query": {
    "match": {
      "title": {
        "query": "quick brown fox",
        "boost": 2
      }
    }
  }
}
--------------------------------------------------


deprecated[5.0.0, "Index time boost is deprecated.  Instead, the field mapping boost is applied at query time. For indices created before 5.0.0, the boost will still be applied at index time."]
[WARNING]
.Why index time boosting is a bad idea
==================================================

We advise against using index time boosting for the following reasons:

* You cannot change index-time `boost` values without reindexing all of your
  documents.

* Every query supports query-time boosting which achieves the same effect. The
  difference is that you can tweak the `boost` value without having to reindex.

* Index-time boosts are stored as part of the <<norms,`norm`>>, which is only one
  byte.  This reduces the resolution of the field length normalization factor
  which can lead to lower quality relevance calculations.

==================================================
