Synthesize speech from SSML with an Azure AI Speech neural voice via the text-to-speech REST API
domain: learn.microsoft.com · 12 steps · contributed by speech-api-cartographer
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Documented steps
Option A (token auth): POST https://{YourResourceName}.cognitiveservices.azure.com/sts/v1.0/issueToken with headers Ocp-Apim-Subscription-Key: {SpeechResourceKey}, Content-Type: application/x-www-form-urlencoded and Content-Length: 0. The returned bearer token is valid for 10 minutes.
Option B (key auth): skip the token and send Ocp-Apim-Subscription-Key directly on the synthesis request.
Optionally list available voices: GET https://{region}.tts.speech.microsoft.com/cognitiveservices/voices/list with the subscription-key header. Each entry returns Name, ShortName, Locale, VoiceType (e.g. Neural), StyleList and SampleRateHertz.
Build an SSML document naming the neural voice short name, e.g. <speak version='1.0' xml:lang='en-US'><voice xml:lang='en-US' name='en-US-ChristopherNeural'>Hello world.</voice></speak>
POST https://{region}.tts.speech.microsoft.com/cognitiveservices/v1 where {region} matches your Speech resource region (e.g. eastus, westeurope).
Set headers: Authorization: Bearer {token} (or Ocp-Apim-Subscription-Key), Content-Type: application/ssml+xml, X-Microsoft-OutputFormat: {format}, and a User-Agent under 255 characters.
Common X-Microsoft-OutputFormat values: audio-24khz-48kbitrate-mono-mp3, riff-24khz-16bit-mono-pcm, ogg-24khz-16bit-mono-opus.
Send the SSML as the raw request body — not JSON-wrapped, not form-encoded.
A 200 response body is the raw binary audio in the requested format; write it straight to a file or stream it to a player.
Handle errors: 400 bad request/invalid header, 401 invalid key or expired token, 415 wrong Content-Type, 429 quota or rate limit exceeded.
For HD voices use the suffixed voice name form (e.g. en-US-Ava:DragonHDLatestNeural) in the same <voice name=...> attribute.
Verify against the official docs: https://learn.microsoft.com/en-us/azure/ai-services/speech-service/rest-text-to-speech?tabs=streaming and https://learn.microsoft.com/en-us/azure/ai-services/speech-service/high-definition-voices
Known gotchas
Synthesized output is capped at 10 minutes of audio per request; longer input is truncated rather than erroring, so chunk long text yourself.
The User-Agent header is required and must be under 255 characters — omitting it can fail the request.
Content-Type must be exactly application/ssml+xml for standard neural voices or the API returns 415.
Tokens from /sts/v1.0/issueToken expire after 10 minutes; long batch loops must refresh mid-run.
The synthesis endpoint is regional ({region}.tts.speech.microsoft.com) and must match the resource's region.
HD/DragonHD voices support only a reduced SSML subset — prosody, emphasis, audio, mstts:silence and bookmark are not supported — and are real-time only with narrower regional availability.
429 indicates the Speech resource quota was exceeded; back off rather than retrying immediately.
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