[[breaking_60_rest_changes]]
=== REST changes

==== Unquoted JSON

In previous versions of Elasticsearch, JSON documents were allowed to contain unquoted field names.
This feature was removed in the 5.x series, but a backwards-compatibility layer was added via the
system property `elasticsearch.json.allow_unquoted_field_names`. This backwards-compatibility layer
has been removed in Elasticsearch 6.0.0.

==== Duplicate Keys in JSON, CBOR, Yaml and Smile

In previous versions of Elasticsearch, documents were allowed to contain duplicate keys. Elasticsearch 6.0.0
 enforces that all keys are unique. This applies to all content types: JSON, CBOR, Yaml and Smile.

==== Content-Type Auto-detection

In previous versions of Elasticsearch, having a proper Content-Type for the data in a request was not enforced.
Elasticsearch 6.0.0 enforces that all requests with a body must have a supported Content-Type and this type will
be used when parsing the data.

When using the `source` query string parameter, the `source_content_type` parameter must also be specified with
the media type of the source.

==== Boolean API parameters

All REST APIs parameters (both request parameters and JSON body) support providing boolean "false" as the
value `false` and boolean "true" as the value `true`. All other values will raise an error.

==== Analyze API changes

The deprecated request parameters and plain text in request body has been removed. Define parameters in request body.

==== Indices exists API

The `ignore_unavailable` and `allow_no_indices` options are no longer accepted
as they could cause undesired results when their values differed from their
defaults.

==== `timestamp` and `ttl` in index requests

`timestamp` and `ttl` are not accepted anymore as parameters of index/update
requests.

==== Refresh requests with one or more shard failures return HTTP 500 response instead of 200

Refresh requests that are broadcast to multiple shards that can have one or more
shards fail during the request now return a 500 response instead of a 200
response in the event there is at least one failure.

=== Delete by Query API requires an explicit query

In previous versions of Elasticsearch, delete by query requests without an explicit query
were accepted, match_all was used as the default query and all documents were deleted
as a result. From version 6.0.0, delete by query requests require an explicit query.
