---
title: "structured_metadata | Grafana Loki documentation"
description: "The 'structured_metadata' Promtail pipeline stage"
---

> For a curated documentation index, see [llms.txt](/llms.txt). For the complete documentation index, see [llms-full.txt](/llms-full.txt).

# structured\_metadata

> Warning
> 
> Structured metadata is an experimental feature and is subject to change in future releases of Grafana Loki.

The `structured_metadata` stage is an action stage that takes data from the extracted map and modifies the [structured metadata](../../../../get-started/labels/structured-metadata/) that is sent to Loki with the log entry.

> Warning
> 
> Structured metadata will be rejected by Loki unless you enable the `allow_structured_metadata` per tenant configuration (in the `limits_config`).

## Schema

YAML ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```yaml
structured_metadata:
  # Key is REQUIRED and the name for the label of structured metadata that will be created.
  # Value is optional and will be the name from extracted data whose value
  # will be used for the value of the label. If empty, the value will be
  # inferred to be the same as the key.
  [ <string>: [<string>] ... ]
```

### Examples

For the given pipeline:

YAML ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```yaml
- json:
    expressions:
      stream: stream
      traceID: traceID
- labels:
    stream:
- structured_metadata:
    traceID:
```

Given the following log line:

![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```none
{"log":"log message\n","stream":"stderr","traceID":"0242ac120002",time":"2019-04-30T02:12:41.8443515Z"}
```

The first stage would extract `stream` with a value of `stderr` and `traceID` with a value of `0242ac120002` into the extracted data set. The `labels` stage would turn that `stream` and `stderr` key-value pair into a stream label. The `structured_metadata` stage would attach the `traceID` and `0242ac120002` key-value pair as a structured metadata to the log line.