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Supported Languages & Features

For the complete documentation index, see llms.txt

AssemblyAI supports a wide range of languages across our speech-to-text models for pre-recorded audio. The available languages and features vary by model. Check out the Models page to learn more about our different models and how to choose the best one for your use case. See our Model selection page for more details on specifying a model in your request.

Unsupported feature behavior

Not all features are available for every language. If you enable a feature that isn't supported for the language of your audio, the API's behavior depends on how the language was specified:

• With language_code (manual): The API rejects the request and returns an error, such as "The following models are not available in this language: speaker_labels". This lets you catch configuration issues before processing.
• With language_detection (automatic): The request completes normally, but any features that aren't supported for the detected language are silently omitted from the response. The transcription itself still succeeds. This is because the language isn't known until after the request is submitted, so the API can't validate feature compatibility upfront.

To avoid unexpected results when using Automatic Language Detection, check the feature tables below to confirm which features are available for the languages you expect in your audio. You can also use the language_code and language_confidence fields in the response to verify the detected language and handle cases where a feature may not have been applied.

Universal-3 Pro

Regional dialects and variants

Universal-3 Pro goes beyond standard language support with deep understanding of regional dialects and local variants. Whether your audio features Quebecois French, Mexican Spanish, or Brazilian Portuguese, the model accurately captures speech as it's naturally spoken — including colloquial expressions, local vocabulary, and accent-specific pronunciation patterns.

You do not need to specify a dialect code to get accurate dialect transcription. Universal-3 Pro automatically recognizes regional speech patterns when using the base language code (e.g., fr for all French dialects, es for all Spanish dialects).

Dialect / Variant	Description
American English	Standard US English, including regional variants (Southern, Midwestern, Northeastern)
British English	UK English, including Received Pronunciation and regional accents
Australian English	Australian English with local expressions and pronunciation

Dialect / Variant	Description
Castilian Spanish	Standard Peninsular Spanish as spoken in central and northern Spain
Mexican Spanish	Mexican Spanish with local vocabulary and pronunciation
Argentine Spanish	Rioplatense Spanish with distinctive voseo and pronunciation
Colombian Spanish	Colombian Spanish with regional speech patterns
Chilean Spanish	Chilean Spanish with rapid speech patterns and local slang
Caribbean Spanish	Cuban, Dominican, and Puerto Rican Spanish dialects
Spanglish	English-Spanish code-mixing common in US bilingual communities

Dialect / Variant	Description
Metropolitan French	Standard Parisian French
Canadian French (Quebecois)	Quebec French with distinctive vocabulary, pronunciation, and expressions
Belgian French	Belgian French with local vocabulary and pronunciation

Dialect / Variant	Description
Brazilian Portuguese	Brazilian Portuguese with local vocabulary, pronunciation, and expressions
European Portuguese	Standard Lisbon Portuguese with Iberian pronunciation

Dialect / Variant	Description
Standard Italian	Standard Italian based on Tuscan-influenced speech

Universal-2

Breakdown of Universal-2 language support

English, Spanish, French, German, Indonesian, Italian, Japanese, Dutch, Polish, Portuguese, Russian, Swedish, Turkish, Ukrainian, Catalan

Arabic, Azerbaijani, Bulgarian, Bosnian, Mandarin Chinese, Czech, Danish, Greek, Estonian, Finnish, Galician, Hebrew, Hindi, Croatian, Hungarian, Korean, Macedonian, Malay, Norwegian, Romanian, Slovak, Swiss German, Tagalog, Thai, Urdu, Vietnamese

Afrikaans, Belarusian, Welsh, Persian (Farsi), Armenian, Icelandic, Kazakh, Lithuanian, Latvian, Maori, Marathi, Slovenian, Swahili, Tamil

Amharic, Assamese, Bengali, Gujarati, Hausa, Javanese, Georgian, Khmer, Kannada, Luxembourgish, Lingala, Lao, Malayalam, Mongolian, Maltese, Burmese, Nepali, Occitan, Punjabi, Pashto, Sindhi, Shona, Somali, Serbian, Telugu, Tajik, Uzbek, Yoruba