YouTube announced on its blog today that it has added a new tool allowing users to blur out the faces in an uploaded video. The site wants to give anonymity to users that might fear reprisal by public viewers. "Whether you want to share sensitive protest footage without exposing the faces of the activists involved, or share the winning point in your 8-year-old’s basketball game without broadcasting the children’s faces to the world, our face blurring technology is a first step towards providing visual anonymity for video on YouTube," the site's post announced.

After you upload the original video, YouTube's Video Enhancements tool will lead you to "Additional features." Here you can click apply under "Blur All Faces." Checking "Delete original video" will then trash your copy of the video with exposed faces.

Currently, YouTube warns that the technology is imperfect, and may leave some faces un-blurred. But you can view the video before you post it. If the tool did not catch all of the faces, you can choose to keep the video private. Also, the tool can only blur out every face in a video, so you can't single out faces for blurring, and leave the identities of others exposed to the world. Jessica Mason, a spokesperson for YouTube, wrote to Ars in an e-mail that the company was working on improving the technology and creating new features in the future.

The technology may be imperfect on YouTube's site, but the pieces that make up the technology are hardly new. "We use an algorithm that scans a video and detects facial features like eyes. From there it blurs the detected faces by adding things like noise and pixelation to the detected features," Mason wrote. Facebook has been using face detection technology in its photos since last year, and offline video editors have been able to blur faces for much, much longer than that.

But better late than never. Considering YouTube's importance in disseminating citizen journalism, the feature will likely be useful to people with kids, or anyone who wants to stay under the radar while still making certain actions public. Of course, YouTube's Community Guidelines "prohibit illegal content or material that incites violence," so you still won't be seeing tours of anyone's 2,000 sq ft meth lab anytime soon.

Mason told Ars that YouTube began to "seriously discuss and pursue" the feature at the 2011 Silicon Valley Human Rights Conference. She also credited activists and human rights organizations, specifically the 2011 Witness Cameras Everywhere report, for pushing for this kind of feature.

In a quick test of the feature, we found that YouTube is right—the blur tool does work imperfectly, but it's better than nothing. Applying the blur effect went very quickly on an 18 second clip, although obviously the longer your video is, the longer you'll be waiting for the edit to resolve (ultimately it will depend on your Internet connection, though).

Before using the tool, my clip had a few moments where the camera was shaky. When the image was particularly poor, but YouTube's algorithm still detected a face, the blur tool would blur out large swaths of the image, in a hilarious (or frustrating) case of over-correction. And when only half of a face was visible, the blur tool wouldn't work at all. For some it may be better to obscure more of the image than less, but if you're marching in a demonstration or jogging down the touchlines of your kid's soccer game, be aware that using YouTube's tool on irreparably shaky video might negate the whole purpose of videotaping the event.

Still, for fast and free anonymity, YouTube's new feature is incredibly easy, and will certainly go a long way toward hiding identities in a world of seemingly ubiquitous cameras.

Update: YouTube's Jessica Mason responded to our inquiry into how possible or easy it is to undo the blur effect on their videos. Regarding unblurring, "We can't say it's impossible to unblur, but we have made it incredibly difficult," Mason told Ars in an e-mail late Wednesday evening. "We feel we've made it so difficult that it's not worth the immense effort required to try." In addition, Mason noted that after the original video is deleted, the unblurred version is completely gone from Google's servers "very quickly."