You can use the update settings API operation to update index-level settings. You can change dynamic index settings at any time, but static settings cannot be changed after index creation. For more information about static and dynamic index settings, see [Create index]({{site.url}}{{site.baseurl}}/api-reference/index-apis/create-index).
Aside from the static and dynamic index settings, you can also update individual plugins' settings. To get the full list of updatable settings, run `GET <target-index>/_settings?include_defaults=true`.
allow_no_indices | Boolean | Whether to ignore wildcards that don’t match any indexes. Default is `true`.
expand_wildcards | String | Expands wildcard expressions to different indexes. Combine multiple values with commas. Available values are `all` (match all indexes), `open` (match open indexes), `closed` (match closed indexes), `hidden` (match hidden indexes), and `none` (do not accept wildcard expressions), which must be used with `open`, `closed`, or both. Default is `open`.
flat_settings | Boolean | Whether to return settings in the flat form, which can improve readability, especially for heavily nested settings. For example, the flat form of “index”: { “creation_date”: “123456789” } is “index.creation_date”: “123456789”.
ignore_unavailable | Boolean | If true, OpenSearch does not include missing or closed indexes in the response.
preserve_existing | Boolean | Whether to preserve existing index settings. Default is false.
master_timeout | Time | How long to wait for a connection to the master node. Default is `30s`.
timeout | Time | How long to wait for a connection to return. Default is `30s`.
## Request body
The request body must all of the index settings that you want to update.