Index name syntax

Many OpenSearch REST APIs accept one or more index names in the request path. You can target several indexes in one request, select indexes by date using date math, and prevent requests from specifying indexes in the request body.

Targeting multiple indexes

Most APIs that accept an index name in the path can run on several indexes at once. Specify the target indexes in one of the following ways:

• A comma-separated list of names, for example, app-logs-2026.10.12,app-logs-2026.10.13.
• A wildcard pattern, for example, app-logs-* or *-logs-*.
• _all or * to target all indexes.
• An exclusion, which removes indexes from the preceding patterns. Prefix the name or pattern with -, for example, app-logs-*,-app-logs-2026.10.11. An exclusion must follow at least one inclusive name or pattern. A path containing only -app-logs-2026.10.11 is interpreted as the literal index name -app-logs-2026.10.11.

The following request counts the documents in all app-logs- indexes created in 2026, except app-logs-2026.10.11:

GET /app-logs-2026*,-app-logs-2026.10.11/_count

APIs that operate on a single document or a single index, such as the Index Document API, do not accept multiple indexes. A comma-separated list in the path of these APIs is rejected as an invalid index name.

APIs that support multiple indexes accept the following query parameters, which control how OpenSearch resolves the target indexes. The default values depend on the API.

Date math in index names

If you create one index per day or month for time-series data, you can use date math in the request path to select indexes by their date. For example, a request can target only this month’s and last month’s sales indexes without your client calculating their names, and OpenSearch reads only those indexes. Most APIs that accept an index name in the path support date math. For example, you can use date math to name the indexes created by a rollover. For more information, see Using date math with index rollovers.

A date math index name has the following format:

<static_name{date_math_expression{date_format|time_zone}}>

The following table describes the components of a date math index name.

The entire expression must be enclosed in angle brackets. To use { or } in the static part of the name, escape the character using a backslash (\).

The following table shows how expressions resolve if the current time is 18:00 UTC on October 13, 2026.

OpenSearch resolves date math using the Gregorian calendar, regardless of the locale.

In a request URL, you must percent-encode the special characters in a date math expression. OpenSearch rejects a URL that contains these characters without encoding. The following table lists the encoded value of each character.

The following request calculates the total west region sales from the monthly sales- indexes for the current and previous months. Before encoding, the index part of the path is <sales-{now/M-1M{yyyy-MM}}>,<sales-{now/M{yyyy-MM}}>:

GET /%3Csales-%7Bnow%2FM-1M%7Byyyy-MM%7D%7D%3E%2C%3Csales-%7Bnow%2FM%7Byyyy-MM%7D%7D%3E/_search
{
  "size": 0,
  "query": {
    "term": {
      "region": "west"
    }
  },
  "aggs": {
    "total_sales": {
      "sum": {
        "field": "amount"
      }
    }
  }
}

Restricting indexes in request bodies

The Bulk, Multi-get, and Multi-search APIs let each item in the request body specify its own target index, overriding the index in the request path. If you control access to indexes based on the request URL, for example, using a proxy, a user could bypass that control by naming a different index in the request body.

To prevent this, set rest.action.multi.allow_explicit_index to false in opensearch.yml on each node. This is a static setting, so you must restart the node for it to take effect. Default is true. When the setting is false, these APIs reject any request whose body specifies an index, even if it matches the index in the path. Specify the target index in the request path:

POST /orders/_bulk
{ "index": {} }
{ "product": "Trail running shoes" }

Related documentation

• Common REST parameters
• Supported units
• Cron expressions