YouTube is rolling out automatic captions to millions of the clips hosted on the video-sharing site.
The Google-owned site trialled automatic captions on a handful of videos from the University of California, Yale University and National Geographic last November in a bid to make the site more accessible to the deaf and hard of hearing.
YouTube said it plans to add automatic captions to all of its nine million English-language videos, with other languages following in the coming months.
It warned web users the service wasn't perfect and where necessary a transcript of the video will be made available for download to improve the experience.
The automatic captions are created using Google's Voice search which analyses the audio track of the video clip.
"Twenty hours of video is uploaded to YouTube every minute. Making some of these videos more accessible to people who have hearing disabilities or who speak different languages, not only represents a significant advancement in the democratisation of information, it can also help foster greater collaboration and understanding," said YouTube's product manager, Hiroto Tokusei, in a blog.
Emma Harrison from the Royal National Institute for the Deaf (RNID) added: "Captioning will significantly help people with a hearing loss understand video content and increase their ability to share experiences of watching those in which speech plays a prominent part."
YouTube also said there would be a "request processing" button that allows web users to request a video be captioned. Tokusei said this would, in some cases, "speed up the availability of auto-captions".