
Earlier this year, a group of climate scientists were outraged about a Wall Street Journal editorial. In an earlier era, they might have written a letter to the editor, or meekly submitted their opinion piece for publication. Instead, they did what scholars have long done in academic circles: they annotated the WSJ broadside. Using an open source tool called Hypothesis, they highlighted examples of what they referred to as "willful ignorance of the science," and "misguided notions," and posted comments rebutting the offending passages. Today, if you read the article using the Hypothesis browser extension or by following a Hypothesis link, you can review highlighted passages and more than 50 detailed annotations provided by the climate scientists.
The climate scientists are far from alone in their enthusiasm about annotating the web. This year, the White House provided an annotated version of President Obama's State of the Union using Genius, an annotation platform that also has been used by, among others, the U.S. Geological Survey (which marked up a report on "The Decline in Amphibian Population in the United States") and actor Ashton Kutcher (who annotated several speeches by Steve Jobs while playing the Apple co-founder in a 2013 biopic).
The service, which started in 2009 as Rap Genius, a website that allowed rap music fans to annotate lyrics, expanded into news annotation with News Genius in 2013, and now provides a browser extension that lets anyone add comments to any web site. Its slogan: "Annotate the world."
"I think web annotation is coming like a locomotive," says Dan Whaley, Hypothesis' founder and CEO. "And it's not just a specialized thing for academics or educators. It's a uniform collaborative layer over the whole web."
Today's annotation tools—which don't actually mark up websites, but rather add highlights and comments in an external layer that you typically view using a special link or browser extension — are heirs to a concept that dates back to the dawn of the web. As Genius co-founder and president Ilan Zechory points out, Marc Andreessen, the pioneering developer who created the first modern web browser in the early 90s, saw annotation as "a central part of his idea of what the web browser was." Andreessen eventually dropped annotation from his first browser, Mosaic, and it never made it into its successor, Netscape. "The computing resources needed for the kind of social annotation he envisioned weren't available at the time and were very difficult to engineer," says Zechory.
That didn't stop other early developers from trying. Third Voice, founded by a group of Singaporean engineers in 1998, raised more than $5 million in its first year, and saw itself as a tool to "empower users" and make the web "more meaningful." It didn't quite work out that way. An article in Wired likened Third Voice annotations to graffiti, and one in Salon pointed out that the platform "offers great potential for abuse and defamation." According to Leo Jolicoeur, who was the company's vice president for business development, Third Voice could never get past the idea that its software wasn't good for much more than vandalizing innocent web sites. "It was seen as a layer of chaos on top of the web," he recalls. Although Third Voice tried to reposition itself as a more focused discussion service, "we were burdened by that early response," Jolicoeur recalls. "We were never able to recover from that position." The company shut its doors in 2001.
Nearly a decade later, Google entered the fray with SideWiki, an annotation tool launched in 2009 and discontinued two years later. Critics of SideWiki included journalist and author Jeff Jarvis, who worried that the service would undermine the value of annotated web sites, since the commentary would exist independently of the underlying content. "On a practical level, only people who use the Google Toolbar will see the comments left using it and so it bifurcates the conversation and puts some of it behind a hedge," he wrote on his blog, BuzzMachine. He also questioned the ethics of SideWiki, comparing it to early services that would wrap a frame around content on other sites and sell ads against it.
Can services like Genius and Hypothesis succeed where Third Voice and SideWiki failed? In some ways, they're already more successful. Hypothesis, a nonprofit whose backers include both major foundations and small Kickstarter donors, has formed a coalition that includes more than 60 major academic publishers and institutions. The organization's officers and advisors are a who's who of internet pioneers, including Electronic Frontier Foundation co-founder John Perry Barlow and the Internet Archive's Brewster Kahle.
Genius, meanwhile, has raised more than $50 million from investors, including Andreessen, whose VC firm, Andreessen Horowitz, was an early backer. The company recently announced a deal with streaming music service Spotify to build annotation functionality into playlists. And in March Genius announced plans to start selling ads around its annotations.

Unlike some earlier annotation providers, Hypothesis and Genius also are working to build closer relationships with publishers. Both provide tools that allow sites to embed annotations directly into content, essentially replacing traditional commenting systems. Both also are active in finding ways to make sure annotation doesn't interfere with the underlying functionality of annotated websites, including their ability to display ads. "We're very committed to keeping publishers happy and keeping the advertisers who run on those publishers happy," says Zechory. (As Genius begins selling advertising, Zechory admits that the company will need to address issues like how to identify paid annotations from brands. "If a brand is paying to use the Web Annotator in some way, we'll make that really clear.")
Supporters of annotation see the tools as a way to democratize the web, correct the public record, and provide context and background on everything from music lyrics to daily news reports. News Genius Managing Editor Leah Finnegan calls annotators "rogue public editors," and sees the service as a way for independent commenters to point out "bad journalism" and biased reporting. At the same time, the company encourages journalists to use annotations to add more depth to their work, something Zechory likens to a web version of "DVD extras." The service has won praise from some journalists, including The Washington Post's Chris Cillizza, who says it gives him "the ability to look at a primary source document and comment on it, add some depth to it and do it along with a bunch if other interested and interesting people."
Genius also has critics who have voiced some of the same concerns raised about earlier services such asThird Voice. In March, blogger Ella Dawson wrote that seeing inappropriate Genius annotations on her personal website was "like discovering graffiti over some of my most personal work," and suggested that the service provide a way for individual sites to opt out of annotation. Rep. Katherine Clark (D-MA) echoed those concerns in a letter to Genius, saying that, "while the ability to post commentary can serve to enhance public discourse, it can also be used as a tool to harass, intimidate and silence." Clark asked if Genius was prepared to "implement a robust reporting and remediation process or provide an opt-out function."
Following Clark's letter, Genius added a button to allow users to report abuse, and also held talks with her office. Zechory characterized the meeting as "a great conversation," and said that "it's great to have a member of Congress who's concerned" about keeping the internet safe. Clark's office called the new button "a step in the right direction." Finnegan says the service is "very tightly moderated" and that she and a deputy "read every single annotation that comes in through the Web Annotator."
The Washington Post's Cillizza acknowledges that internet commentary can "go over the line," and that annotation services must hire moderators "with a keen sense of their community and what flies there (and doesn't)." He also sees annotation as a better option than traditional web comments. "To me, comments sections — at least in political news stories — have failed," he says. "They are filled with name-calling, bullying and spamming. For me, Genius' annotator allows a more edifying and organic conversation about a piece of content. It also doesn't allow a few loud/nasty voices to discourage other people from joining the conversation."
Hypothesis founder Whaley admits that annotation services need to "be more thoughtful about the balance between speaking truth to power, which is one of the potential roles of annotation, and at the other end, acknowledging marginalized voices who are subject to abuse and harassment and may need a little protected space on the internet."
Whaley envisions an environment where website owners could insert code into their sites that would tell annotation providers their preferences. Annotation services, in turn, could ignore those preferences in the name of serving the public interest. "If the Turkish government turns on a flag saying, Please don't annotate our page, the public should be able to override it," Whaley says.
For annotation to succeed as a business and a concept, it will have to move beyond its current status as something of a niche function that most casual internet users aren't exposed to. "Genius is very much an opt-in product," says Zechory. "If you want to read annotations, you have to go to a special URL or install a special extension or go to a publisher that has decided to allow Genius annotations to be exposed." As of late April, the Genius Web Annotator, which launched in January, had been installed by about 7,500 users, according to the Google Chrome Web Store. Hypothesis' annotation tool had about 20,000 users. Using annotation is difficult on mobile browsers, which now account for more than half the traffic of many websites—and annotation tools don't work inside mobile apps such as Facebook or Snapchat.
Both Whaley and Zechory acknowledge that, for annotation to fully succeed, it needs to be incorporated directly into web browsers and the rest of the internet infrastructure, much as Andreessen imagined it in the early 90s. "I think the longest-term future of annotation on the internet has to involve really big partners who own, control and build things like web browsers and devices," says Zechory. Annotation, Whaley says, needs to be "pervasive." He believes Hypothesis' non-commercial route presents a clearer path to that future. "This can't be a proprietary, closed system."
Regardless of whether annotation becomes the kind of ubiquitous function envisioned by its proponents, it's unlikely to go away. And if you want to annotate this article, you can do it here.