Use the isutf8 function to check whether a string is a valid UTF-8 encoded sequence. The function returns a boolean indicating whether the input conforms to UTF-8 encoding rules. isutf8 is useful when working with data from external sources such as logs, telemetry events, or data pipelines, where encoding issues can cause downstream processing to fail or produce incorrect results. By filtering out or isolating invalid UTF-8 strings, you can ensure better data quality and avoid unexpected behavior during parsing or transformation.

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For users of other query languages

If you come from other query languages, this section explains how to adjust your existing queries to achieve the same results in APL.

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Usage

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Syntax

isutf8(value)

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Parameters

NameTypeDescription
valuestringThe input string to validate.

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Returns

A bool value:
  • true if the input string is valid UTF-8.
  • false otherwise.

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Use case examples

You can use isutf8 to detect and exclude malformed UTF-8 entries in HTTP request logs that could indicate issues with upstream data encoding.Query
['sample-http-logs']
| where not(isutf8(uri)) or not(isutf8(method))
| project _time, id, method, uri, status
Run in PlaygroundOutput
_timeidmethoduristatus
2025-07-09T13:32:05Zuser42GET�/broken-path500
2025-07-09T14:10:17Zuser99POST/submit-form%80200
This query identifies records where the uri or method fields contain invalid UTF-8 characters, which may point to upstream client encoding issues or malformed requests.
  • isimei: Checks whether a value is a valid International Mobile Equipment Identity (IMEI) number.
  • isreal: Checks whether a value is a real number.
  • iscc: Checks whether a value is a valid credit card (CC) number.
  • isstring: Checks whether a value is a string. Use this for scalar string validation.