According to WaBetaInfo, WhatsApp has been working on a feature to transcribe voice messages. Before this, it was only possible with the help of third-party apps.
The new feature will reportedly be available to iOS users. The messages will be sent directly to Apple's servers for transcription, instead of WhatsApp or Facebook. The feature will be optional and a permission request will be sent to users before enabling it.
Users will see a new "Transcript" section after enabling the feature, where they can find the transcriptions of past voice messages, complete with timestamps. The transcriptions will be saved locally so users won't have to transcribe again the next time they need the message. There's still no news of the feature's availability for its Android app yet.