OpenAI's Whisper model is an open-source automatic speech recognition (ASR) tool that supports multiple languages and translation into English. It can be easily invoked at the command line, but for better scalability and integration with other software systems, an API is more suitable. This article provides a step-by-step guide on how to build an HTTP API using Python's Flask framework, which allows users to transcribe audio files by sending POST requests containing the file data. The final API can handle multiple submitted files at once and returns JSON responses with transcription results for each file.