Which version of ES was an index created with?

[ndtreviv (Nathan Trevivian)]

Is it possible to see which version of elasticsearch an index was created with?

[DavidTurner]

Yes, this is recorded in the index settings:

GET /i/_settings
# at 2018-11-22T17:21:05.813Z
# curl 'http://localhost:9200/i/_settings'

# ----------------------------------------
# Response:
# 200 OK
# {
#   "i": {
#     "settings": {
#       "index": {
#         "provided_name": "i",
#         "number_of_shards": "1",
#         "uuid": "IymFxH1AS_ivXlVRNuaU3g",
#         "number_of_replicas": "0",
#         "version": {
#           "created": "6020499"
#         },
#         "creation_date": "1542906626369"
#       }
#     }
#   }
# }

6020499 means version 6.2.4 (and the 99 just means it's a release version)