How do I build speech-to-text into my app with an API?

To add speech-to-text (STT) to your app with an API, you generally follow this flow:

1. Capture audio in your app
2. Send the audio to a speech-to-text API
3. Receive transcribed text
4. Display or process the text in your app

Typical architecture

1) Record audio on the client

Use your app’s platform tools to record audio:

• Web: MediaRecorder
• iOS: AVAudioRecorder
• Android: AudioRecord or MediaRecorder
• React Native / Flutter: platform audio recording plugins

Save or stream the audio in a format the API accepts, such as:

• mp3
• wav
• m4a
• webm
• ogg

2) Send audio to your backend or directly to the API

There are two common patterns:

Option A: Client → Your backend → STT API

Best if you want to:

• hide API keys
• add authentication
• log or moderate requests
• process or store audio securely

Option B: Client → STT API directly

Best for prototypes, but only if the API supports secure client-side access. Usually you still avoid exposing secret keys in the browser or mobile app.

3) Call the speech-to-text endpoint

Most STT APIs accept either:

• a file upload
• a streaming audio connection
• a pre-signed URL to audio storage

A simple file-upload request often looks like:

curl https://api.example.com/v1/transcriptions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -F "file=@audio.mp3" \
  -F "language=en"

The response typically includes:

{
  "text": "Hello, this is a test transcription."
}

4) Show the transcript in your app

Use the returned text to:

• display captions
• store meeting notes
• trigger search/indexing
• feed an AI assistant
• analyze sentiment or intent

---

Example backend flow

Node.js example

import express from "express";
import multer from "multer";
import fetch from "node-fetch";
import FormData from "form-data";

const app = express();
const upload = multer({ dest: "uploads/" });

app.post("/transcribe", upload.single("audio"), async (req, res) => {
  try {
    const form = new FormData();
    form.append("file", fs.createReadStream(req.file.path));
    form.append("language", "en");

    const response = await fetch("https://api.example.com/v1/transcriptions", {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.STT_API_KEY}`,
        ...form.getHeaders(),
      },
      body: form,
    });

    const data = await response.json();
    res.json(data);
  } catch (err) {
    res.status(500).json({ error: "Transcription failed" });
  }
});

---

Real-time speech-to-text

If you want live captions while someone is speaking, use a streaming STT API. These usually work over:

• WebSockets
• gRPC
• WebRTC
• vendor-specific streaming endpoints

This is better for:

• live captions
• voice assistants
• call transcription
• dictation apps

In streaming mode, you:

1. open a live audio connection
2. send small audio chunks continuously
3. receive partial transcripts in real time

---

Key features to look for in an STT API

When choosing an API, check for:

• Accuracy
• Streaming support
• Speaker diarization (who said what)
• Language support
• Punctuation and casing
• Word timestamps
• Noise robustness
• Custom vocabulary
• Cost per minute
• Latency
• Privacy / compliance

---

Common providers

Some popular speech-to-text API providers include:

• OpenAI
• Google Cloud Speech-to-Text
• AWS Transcribe
• Azure Speech
• Deepgram
• AssemblyAI

---

Best practices

• Compress audio if possible to reduce upload size
• Use 16 kHz mono for speech when supported
• Handle long recordings by chunking or streaming
• Send clear error messages for unsupported formats
• Protect API keys on the server
• Consider privacy laws if processing user voice data

---

Minimal implementation plan

If you want the fastest path:

1. Add audio recording to your app
2. Upload the audio to your server
3. Forward it to an STT API
4. Return the transcript to the client
5. Display it in your UI

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If you want, I can also give you:

• a web app example
• a Node.js backend example
• a Python backend example
• or a real-time streaming example