curl --request POST \
--url https://api.impossibl.com/v1/audio/speech \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '
{
"input": "<string>",
"voice": "eve",
"speed": 1
}
'import requests
url = "https://api.impossibl.com/v1/audio/speech"
payload = {
"input": "<string>",
"voice": "eve",
"speed": 1
}
headers = {
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
body: JSON.stringify({input: '<string>', voice: 'eve', speed: 1})
};
fetch('https://api.impossibl.com/v1/audio/speech', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://api.impossibl.com/v1/audio/speech",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'input' => '<string>',
'voice' => 'eve',
'speed' => 1
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://api.impossibl.com/v1/audio/speech"
payload := strings.NewReader("{\n \"input\": \"<string>\",\n \"voice\": \"eve\",\n \"speed\": 1\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://api.impossibl.com/v1/audio/speech")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"input\": \"<string>\",\n \"voice\": \"eve\",\n \"speed\": 1\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://api.impossibl.com/v1/audio/speech")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"input\": \"<string>\",\n \"voice\": \"eve\",\n \"speed\": 1\n}"
response = http.request(request)
puts response.read_body"<string>"{
"error": {
"message": "`model` and `messages` are required",
"type": "invalid_request_error"
}
}{
"error": {
"message": "Invalid API key",
"type": "authentication_error"
}
}{
"error": {
"message": "Insufficient credits. Top up to continue.",
"type": "insufficient_quota"
}
}{
"error": {
"message": "Unknown model: foo/bar",
"type": "invalid_request_error"
}
}{
"error": {
"message": "permission-denied: ...",
"type": "upstream_error"
}
}{
"error": {
"message": "Provider not configured: missing OPENAI_API_KEY",
"type": "provider_not_configured"
}
}Synthesize speech from text
OpenAI-compatible text to speech. The response body is the raw audio.
voice takes the provider’s own voice ids, never OpenAI aliases; GET
/v1/models lists the voices and endpoint for each speech model.
Formats differ by model because the providers do. xai/grok-voice-tts-1.0
encodes natively (mp3, wav, pcm) and bills 15.00per1Minputcharacters,cappedat15,000charactersperrequest.ThetwoGeminiFlashTTSmodels,‘google/gemini−3.8−flash−tts‘and‘google/gemini−3.1−flash−tts−preview‘,emit24kHzmonoPCMonly,sotheyservewav(aheaderoverthatPCM)andpcm,andbilltokensat1.00/1M in and $20.00/1M out.
curl --request POST \
--url https://api.impossibl.com/v1/audio/speech \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '
{
"input": "<string>",
"voice": "eve",
"speed": 1
}
'import requests
url = "https://api.impossibl.com/v1/audio/speech"
payload = {
"input": "<string>",
"voice": "eve",
"speed": 1
}
headers = {
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
body: JSON.stringify({input: '<string>', voice: 'eve', speed: 1})
};
fetch('https://api.impossibl.com/v1/audio/speech', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://api.impossibl.com/v1/audio/speech",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'input' => '<string>',
'voice' => 'eve',
'speed' => 1
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://api.impossibl.com/v1/audio/speech"
payload := strings.NewReader("{\n \"input\": \"<string>\",\n \"voice\": \"eve\",\n \"speed\": 1\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://api.impossibl.com/v1/audio/speech")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"input\": \"<string>\",\n \"voice\": \"eve\",\n \"speed\": 1\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://api.impossibl.com/v1/audio/speech")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"input\": \"<string>\",\n \"voice\": \"eve\",\n \"speed\": 1\n}"
response = http.request(request)
puts response.read_body"<string>"{
"error": {
"message": "`model` and `messages` are required",
"type": "invalid_request_error"
}
}{
"error": {
"message": "Invalid API key",
"type": "authentication_error"
}
}{
"error": {
"message": "Insufficient credits. Top up to continue.",
"type": "insufficient_quota"
}
}{
"error": {
"message": "Unknown model: foo/bar",
"type": "invalid_request_error"
}
}{
"error": {
"message": "permission-denied: ...",
"type": "upstream_error"
}
}{
"error": {
"message": "Provider not configured: missing OPENAI_API_KEY",
"type": "provider_not_configured"
}
}Authorizations
Gateway API key (imp-rt-...) from POST /v1/accounts or /v1/keys.
Body
xai/grok-voice-tts-1.0, google/gemini-3.8-flash-tts, google/gemini-3.1-flash-tts-preview Text to speak. Both models accept inline expressive tags.
A voice id the chosen model supports (see GET /v1/models).
"eve"
Defaults to the model's native format: mp3 for xai, wav for google. A format the model cannot produce is a 400, never a substitution.
mp3, wav, pcm Playback rate, xai/grok-voice-tts-1.0 only. Gemini has no rate control, so any value other than 1 is a 400 there rather than a silently ignored parameter.
0.7 <= x <= 1.5Response
The synthesized audio.
The response is of type file.

