Fifteen percent of tech workers have been silenced by non-disclosure agreements. Thirty-one percent have witnessed or experienced sexual harassment in the workplace. Another 36% have encountered discrimination at work. And 70% of workers in the tech industry said they can't trust HR. How do we know all this? We know because Blind, the anonymous work talk app, asked them.

Originally a South Korean company, Blind expanded to the United States in 2015, after some of its early users exposed a Korean Air CEO for assaulting an employee who served nuts in a bag rather than on a plate during a flight. (The incident has since been dubbed the "nut rage incident" or "nutgate.") Since the app made its way to America, it has acquired users from more than 70,000 companies, mostly from the tech industry. More than 30,000 employees from Microsoft use the app, as well as another 15,000 from Amazon, 5,000 from Uber and 4,000 from Facebook.

Blind's wide reach among employees and total reliance on their willingness to share has allowed workers to give feedback with fierce candor — something HR has already been trying to grapple with on platforms like Glassdoor.

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Blind can ask thousands and thousands of American employees to chime in on widespread issues in the workplace. When a user opens up the app on a smartphone, he or she lands on a feed of posts from other users, threaded with surveys from Blind itself. It's easy to see a survey question, click on an automated response and keep scrolling. That's what more than 10,000 people did when they told Blind whether they had been silenced by an NDA at their workplace. Almost 12,000 people did the same thing as they made known their distrust of HR.

"This proves to be a good tool for HR because they can actually get a pulse of what's going on in the company and see where the pain points are of employees without running their own surveys," Kyle McCarthy, head of marketing at Blind, said. "It's an unbiased look at what's happening so data can't be skewed by people who want to see specific data at their company."

User posts make up most of the home feed, however. Most of them pertain to work: "How do you answer the question 'why are you looking for a new job'?" one user asks, inviting users to comment with advice. Another wanks to know about the culture at Placed, a company that tracks the success of online ads, as he or she considers a job at its Seattle location.

"People join the app because they want answers about what's happening and [advice about] how to fix their current situations," McCarthy said. In September, Blind added HR Issues as a new section to its Topics, rooms where users can start commonly-themed threads. The topic started off as the apps #MeToo page, but has since transformed into a broader place where workers can vent about and seek help for problems they encounter in the office. This is the only topic in which users can post without displaying their company name. "We want to make it as easy as possible and really empower employees as much as possible," McCarthy said.

Some serious situations and even allegations surface within this topic page. One user wrote that he or she left a job after experiencing sexual harassment, and the perpetrator was now joining the user's new company. More than a hundred other users commented with advice, some sharing similar experiences.

McCarthy said Blind plans to expand into more industries. It's already gaining users in the e-commerce and retail fields, with Walmart employees signing up by the hundreds, and aims to expand into finance and gaming, as well.