extract_json(), extractjson()

Get a specified element out of a JSON text using a path expression.

Optionally convert the extracted string to a specific type.


The extract_json() and extractjson() functions are interpreted equivalently.

extract_json("$.hosts[1].AvailableMB", EventText, typeof(int))


extract_json(jsonPath, dataSource, type)

extractjson(jsonPath, dataSource, type)


  • jsonPath: JSONPath string that defines an accessor into the JSON document.
  • dataSource: A JSON document.
  • type: An optional type literal (for example, typeof(long)). If provided, the extracted value is converted to this type.


This function performs a JSONPath query into dataSource, which contains a valid JSON string, optionally converting that value to another type depending on the third argument.


The [bracket] notation and dot (.) notation are equivalent:

| extend AvailableMB = extract_json("$.hosts[1].AvailableMB", EventText, typeof(int))

| extend AvailableMB = extract_json("$['hosts'][1]['AvailableMB']", EventText, typeof(int))

Performance tips

  • Apply where-clauses before using extract_json()
  • Consider using a regular expression match with extract instead. This can run very much faster, and is effective if the JSON is produced from a template.
  • Use parse_json() if you need to extract more than one value from the JSON.
  • Consider having the JSON parsed at ingestion by declaring the type of the column to be dynamic.