Fact · Speech recognition
Azure's REST speech to text API needs a language parameter in the URL, or the request can fail with a 4xx error.
Checked against its source on October 17, 2026
In the source's own words
“You must append the language parameter to the URL to avoid receiving a 4xx HTTP error.”
Speech to text REST API for short audio, Microsoft Learn (Azure AI Speech), n.d., Query parameters.
Open the original- What it measures
- Use the language code for the audio, such as en-US. Azure does not guess the language for this API.
- What it does not show
- The page lists the supported codes in a separate table, which can change.