OPUS to Text: Convert WhatsApp Voice Notes
WhatsApp voice notes are .opus files. Learn what the format is, why WhatsApp uses it, and how to convert them to searchable text.
You exported a WhatsApp chat and found a folder full of .opus files. What are they, why does WhatsApp use this format, and how do you turn them into readable text?
What is an .opus file
Opus is an audio codec designed for interactive speech and music. It was developed by the Internet Engineering Task Force (IETF) and is an open, royalty-free format.
WhatsApp uses Opus for voice messages because it:
- Compresses audio efficiently (small file sizes)
- Maintains good speech quality at low bitrates
- Is optimized for real-time voice communication
- Works across all platforms (iOS, Android, Web)
When you record a voice note in WhatsApp, it is saved as an .opus file.
What .opus files look like in a WhatsApp export
When you export a WhatsApp chat with media included, the .zip contains:
```
WhatsApp Chat - Group Name/
├── _chat.txt
├── 00000001-AUDIO-2024-03-15-09-30-22.opus
├── 00000002-AUDIO-2024-03-15-10-45-11.opus
├── 00000003-PHOTO-2024-03-15-11-00-33.jpg
└── ...
```
Each .opus file corresponds to a voice message in the chat. The filename contains a sequence number and timestamp.
In the _chat.txt file, voice messages appear as:
```
[15/03/2024, 09:30:22] Alice: <attached: 00000001-AUDIO-2024-03-15-09-30-22.opus>
```
Why you cannot just play .opus files
Most computers and phones can play .opus files with the right app. VLC, for example, handles Opus natively. But playing each voice note one by one and taking notes is impractical when you have 20 or 50 voice messages.
The real problem is not playback — it is turning all those voice notes into searchable, analyzable text. A dedicated OPUS to text converter handles this automatically.
How to convert .opus to text
Manual approach
- Open each .opus file in a media player
- Listen and type out the content
- Insert the text into the conversation at the right position
This is accurate but extremely time-consuming. A 2-minute voice note takes 5-10 minutes to transcribe manually.
Using ThreadRecap
- Export your WhatsApp chat with media (include the .opus files)
- Upload the .zip file to ThreadRecap
- ThreadRecap automatically detects all .opus files
- Each voice note is transcribed using OpenAI Whisper
- Transcriptions are inserted into the conversation timeline
The result is a complete conversation where voice notes and text messages flow together in chronological order.
What happens to the audio quality
WhatsApp records voice notes at relatively low bitrates to keep file sizes small. A 1-minute voice note is typically 50-100 KB. Despite this compression, modern speech recognition handles WhatsApp audio well.
Factors that affect transcription quality:
- Background noise — Quiet recordings transcribe best
- Speaking clarity — Clear speech produces better results
- Language — Major languages (English, Spanish, Portuguese, etc.) have the highest accuracy
- Multiple speakers — If someone else is talking in the background, accuracy drops
Opus vs other audio formats
WhatsApp specifically chose Opus over alternatives:
- MP3: Larger files, not optimized for speech
- AAC: Good quality but not open-source
- Opus: Best compression-to-quality ratio for speech, open standard
Some older WhatsApp exports may contain .m4a files instead of .opus — this depends on the WhatsApp version and device. The voice-to-text tool handles both formats.
The bottom line
.opus files are just voice notes in an efficient audio format. The challenge is not the format itself but the volume — when a conversation has dozens of voice notes, manually listening to each one is not practical.
Automated transcription turns those .opus files into text that can be searched, summarized, and analyzed alongside the rest of the conversation.