# todynamic



Use the `todynamic` function to parse a string as a dynamic value, such as a JSON object or array. This function is especially useful when your dataset contains structured data in string format and you want to access nested elements, iterate over arrays, or use dynamic-aware functions.

You often find `todynamic` helpful when working with logs, telemetry, or security events that encode rich metadata or nested attributes in stringified JSON. By converting these strings into dynamic values, you can query, filter, and transform the nested fields using APL’s built-in support for dynamic types.

## Usage [#usage]

### Syntax [#syntax]

```kusto
todynamic(value)
```

### Parameters [#parameters]

| Name  | Type   | Description                                           |
| ----- | ------ | ----------------------------------------------------- |
| value | string | A string representing a JSON-encoded object or array. |

### Returns [#returns]

A dynamic value. If the input isn’t a valid JSON string, the function returns `null`.

## Example [#example]

You want to find events that match certain criteria such as URI and status code. The criteria are stored in a stringified dictionary.

**Query**

```kusto
['sample-http-logs']
| extend criteria = '{"uri": "/api/v1/customer/services", "status": "200"}'
| extend metadata = todynamic(criteria)
| where uri == metadata.uri and status == metadata.status
| project _time, id
```

[Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B'sample-http-logs'%5D%20%7C%20extend%20criteria%20%3D%20'%7B%5C"uri%5C"%3A%20%5C"%2Fapi%2Fv1%2Fcustomer%2Fservices%5C"%2C%20%5C"status%5C"%3A%20%5C"200%5C"%7D'%20%7C%20extend%20metadata%20%3D%20todynamic\(criteria\)%20%7C%20where%20uri%20%3D%3D%20metadata.uri%20and%20status%20%3D%3D%20metadata.status%20%7C%20project%20_time%2C%20id%22%7D)

**Output**

| \_time           | id                                   |
| ---------------- | ------------------------------------ |
| Jun 24, 09:28:10 | 2f2e5c40-1094-4237-a124-ec50fab7e726 |
| Jun 24, 09:28:10 | 0f9724cb-fa9a-4a2f-bdf6-5c32b2f22efd |
| Jun 24, 09:28:10 | a516c4e9-2ed9-4fb9-a191-94e2844e9b2a |

## List of related functions [#list-of-related-functions]

* [pack\_array](/apl/scalar-functions/array-functions/pack-array): Use this to combine scalar values into an array. Use `pack_array` when you don’t need named keys and want positional data instead.
* [bag\_keys](/apl/scalar-functions/array-functions/bag-keys): Returns the list of keys in a dynamic dictionary. Use this to inspect or filter contents created by `pack_dictionary`.
* [bag\_pack](/apl/scalar-functions/array-functions/bag-pack): Expands a dictionary into multiple columns. Use it to revert the packing performed by `pack_dictionary`.

## Other query languages [#other-query-languages]

<LanguageComparisons>
  <Accordion title="Splunk SPL users">
    Splunk automatically interprets structured JSON data and allows you to use dot notation directly on fields, without explicit conversion. In APL, you need to explicitly cast a JSON string into a dynamic value using `todynamic`.

    <CodeGroup>
      ```sql Splunk example
      ... | eval json_field = json_extract(raw_field, "$.key")
      ```

      ```kusto APL equivalent
      ... | extend json_field = todynamic(raw_field).key
      ```
    </CodeGroup>
  </Accordion>

  <Accordion title="ANSI SQL users">
    In standard SQL, you typically use `JSON_VALUE`, `JSON_QUERY`, or `CAST(... AS JSON)` to access structured content in string format. In APL, use `todynamic` to convert a string to a dynamic value that supports dot notation and further manipulation.

    <CodeGroup>
      ```sql SQL example
      SELECT JSON_VALUE(raw_column, '$.key') AS value FROM logs;
      ```

      ```kusto APL equivalent
      ['sample-http-logs']
      | extend value = todynamic(raw_column).key
      ```
    </CodeGroup>
  </Accordion>
</LanguageComparisons>