Create a speech-to-text API with OpenAI GPT4o-mini transcribe

Description

This template provides a simple and powerful backend for adding speech-to-text capabilities to any application. It creates a dedicated webhook that receives an audio file, transcribes it using OpenAI's gpt-4o-mini model, and returns the clean text.

To help you get started immediately, you'll find a complete, ready-to-use HTML code example right inside the workflow in a sticky note. This code creates a functional recording interface you can use for testing or as a foundation for your own design.

Who is this for?

• Developers: Quickly add a transcription feature to your application by calling this webhook from your existing frontend or backend code.
• No-code/Low-code builders: Embed a functional audio recorder and transcription service into your projects by using the example code found inside the workflow.
• API enthusiasts: A lean, practical example of how to use n8n to wrap a service like OpenAI into your own secure and scalable API endpoint.

What problem does this solve?

• Provides a ready-made API: Instantly gives you a secure webhook to handle audio file uploads and transcription processing without any server setup.
• Decouples frontend from backend: Your application only needs to know about one simple webhook URL, allowing you to change the backend logic in n8n without touching your app's code.
• Offers a clear implementation pattern: The included example code provides a working demonstration of how to send an audio file from a browser and handle the response—a pattern you can replicate in any framework.

How it works

This solution works by defining a clear API contract between your application (the client) and the n8n workflow (the backend).

1. The client-side technique:

   • Your application's interface records or selects an audio file.
   • It then makes a POST request to the n8n webhook URL, sending the audio file as multipart/form-data.
   • It waits for the response from the webhook, parses the JSON body, and extracts the value of the Transcript key. You can see this exact pattern in action in the example code provided in the workflow's sticky note.

2. The n8n workflow (backend):

   • The Webhook node catches the incoming POST request and grabs the audio file.
   • The HTTP Request node sends this file to the OpenAI API.
   • The Set node isolates the transcript text from the API's response.
   • The Respond to Webhook node sends a clean JSON object ({"Transcript": "your text here..."}) back to your application.

Setup

1. Configure the n8n workflow:
   • In the Transcribe with OpenAI node, add your OpenAI API credentials.
   • Activate the workflow to enable the endpoint.
   • Click the "Copy" button on the Webhook node to get your unique Production Webhook URL.
2. Integrate with the frontend:
   • Inside the workflow, find the sticky note labeled "Example Frontend Code Below". Copy the complete HTML from the note below it.
   • ⚠️ Important: In the code you just copied, find the line const WEBHOOK_URL = 'YOUR WEBHOOK URL'; and replace the placeholder with the Production Webhook URL from n8n.
   • Save the code as an HTML file and open it in your browser to test.

Taking it further

• Save transcripts: Add an Airtable or Google Sheets node to log every transcript that comes through the workflow.
• Error handling: Enhance the workflow to catch potential errors from the OpenAI API and respond with a clear error message.
• Analyze the transcript: Add a Language Model node after the transcription step to summarize the text, classify its sentiment, or extract key entities before sending the response.