OpenAI API
OpenAI's developer platform for GPT models, realtime voice, transcription, and agents
About OpenAI API
The OpenAI API is OpenAI's developer platform for building on its models. Alongside GPT text and reasoning models, it offers file transcription (gpt-transcribe, gpt-4o-transcribe, gpt-4o-mini-transcribe, whisper-1), a speaker-labeling model (gpt-4o-transcribe-diarize), live transcription over the Realtime API, text-to-speech, and voice agents. Billing is pay-as-you-go per token or per minute of audio.
Pros & Cons
Pros
- One API key covers transcription, LLM post-processing, text-to-speech, and realtime voice agents
- gpt-transcribe accepts free-form prompts and keyword lists to steer domain vocabulary
- Low per-minute prices on batch transcription, from about $0.18 per hour with gpt-4o-mini-transcribe
- Large SDK ecosystem and OpenAI-compatible endpoints copied by other providers make switching easy
Cons
- Features are split across models: speaker labels need gpt-4o-transcribe-diarize and word timestamps need whisper-1
- File uploads are capped at 25 MB, so long recordings must be compressed or chunked
- Speaker labeling isn't supported in Realtime transcription sessions
- Live transcription costs about $1 per hour, several times more than streaming-first STT vendors
Key Features
File transcription (gpt-transcribe)
Recommended model for transcribing recorded speech in its original language, with prompt, keyword, and language hints to steer domain terms and multilingual audio.
Speaker diarization model
gpt-4o-transcribe-diarize returns segments with speaker, start, and end times, and can map speakers to up to four known reference voices. Not available in Realtime sessions.
Live transcription
gpt-live-transcribe and gpt-realtime-whisper transcribe audio as it arrives over the Realtime API via WebRTC or WebSocket.
Whisper with word timestamps
whisper-1 supports word and segment timestamps through timestamp_granularities, plus translation of any supported language into English.
Realtime voice models
Speech-to-speech gpt-realtime models and GPT-Live sessions for building conversational voice agents with tools and MCP.
Text and reasoning models
The same API key covers GPT models for summarizing, extracting, or acting on transcripts.
Batch and cost controls
Batch API, prompt caching, and per-project spend limits for production workloads.
Pricing
- gpt-4o-mini-transcribe: about $0.003/min
- gpt-transcribe: about $0.0045/min
- gpt-4o-transcribe: about $0.006/min
- gpt-live-transcribe and gpt-realtime-whisper: about $0.017/min
- gpt-realtime-translate: about $0.034/min
- Text and reasoning models billed per 1M tokens
- Higher rate limits and reserved capacity
- Data residency and zero data retention options
- Dedicated account support
Best For
Transcribe-then-reason pipelines
Transcribe recordings and pass the text to a GPT model for summaries, extraction, or actions in the same account.
Voice agents
Build speech-to-speech agents on the Realtime API or GPT-Live with tool calling.
Multilingual transcription and translation
Transcribe audio in its original language or translate it into English text with whisper-1.
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