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Breaking changes in 6.0edit
This section discusses the changes that you need to be aware of when migrating your application to Elasticsearch 6.0.
Indices created before 6.0edit
Elasticsearch 6.0 can read indices created in version 5.0 or above. An Elasticsearch 6.0 node will not start in the presence of indices created in a version of Elasticsearch before 5.0.
Reindex indices from Elasticseach 2.x or before
Indices created in Elasticsearch 2.x or before will need to be reindexed with
Elasticsearch 5.x in order to be readable by Elasticsearch 6.x. The easiest
way to reindex old indices is to use the reindex API.