[[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.

==== 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.