Agentifact assessment — independently scored, not sponsored. Last verified Mar 6, 2026.
OpenAI Whisper
OpenAI's Whisper is a highly accurate, multilingual speech-to-text API available via the OpenAI platform, supporting 50+ languages at the same flat rate. The managed API handles audio files up to 25MB in mp3, mp4, wav, webm, and other formats, making it straightforward to add transcription to voice agent pipelines. GPT-4o Transcribe and GPT-4o Mini Transcribe are newer variants offering improved accuracy and cost options. Pricing is $0.006/min for Whisper and GPT-4o Transcribe, and $0.003/min for GPT-4o Mini Transcribe, with no volume tiers—ideal for moderate-volume use cases requiring broad language coverage.
Viable option — review the tradeoffs
You need reliable transcription for voice agents handling global users across 50+ languages without managing separate models or servers.
Near-human accuracy on clear audio (WER <50% benchmark), handles noisy real-world files well but splits long audio for context; GPT-4o Mini variant halves cost with minimal accuracy drop.
You want to analyze customer calls, podcasts, or interviews in multiple languages without hiring transcribers or building custom ASR.
Fast (optimized serving), multilingual detection auto-handles language ID; translation to English is single-shot strong but English-only prompts boost precision.
25MB File Limit
Max 25MB per file requires splitting long audio (e.g., hour-long calls); use prompt chaining for context across segments.
No Native Real-Time Streaming
API processes complete files only—delay for live voice agents; chunk audio or poll for 'speaking' detection as workaround.
Whisper wins on raw accuracy + multilingual, AssemblyAI on real-time + diarization.
Broad language coverage, file-based transcription, simple integration.
Live streaming, speaker separation, custom vocabularies.
Trust Breakdown
What It Actually Does
OpenAI Whisper converts spoken audio into written text with high accuracy across dozens of languages, and can also translate non-English speech to English. It processes common audio files like MP3 or WAV through OpenAI's simple API.[1][3][4]
OpenAI's Whisper is a highly accurate, multilingual speech-to-text API available via the OpenAI platform, supporting 50+ languages at the same flat rate. The managed API handles audio files up to 25MB in mp3, mp4, wav, webm, and other formats, making it straightforward to add transcription to voice agent pipelines. GPT-4o Transcribe and GPT-4o Mini Transcribe are newer variants offering improved accuracy and cost options.
Pricing is $0.006/min for Whisper and GPT-4o Transcribe, and $0.003/min for GPT-4o Mini Transcribe, with no volume tiers—ideal for moderate-volume use cases requiring broad language coverage.
Fit Assessment
Best for
- ✓speech-to-text
- ✓transcription
- ✓audio-processing
Not ideal for
- ✗25 MB file size limit per request
- ✗rate limits under high burst load
Known Failure Modes
- 25 MB file size limit per request
- rate limits under high burst load
Score Breakdown
Protocol Support
Capabilities
Governance
- local-execution-option
- open-source-inspection