Retail traders were outraged when Robinhood restricted trading in memes stocks, but the company's IPO filing shows active users still grew by 6 million in the 1st quarter

• Robinhood added 6 million users in the first quarter, despite outrage from retail investors earlier this year.
• Retail traders revolted against the app after it halted buying of GameStop amid the January surge.
• The trading app made its initial public offering filing public Thursday.

Robinhood users were outraged in January when the company halted buying of GameStop and other meme stocks amid an epic rally - but that didn't dissuade 6 million new active users from trading on the app.

According to the company's S-1 filing for its planned initial public offering, the number of monthly active users jumped by 6 million in the first three months of 2021 to 17.7 million from 11.7 million at the end of December - an increase of 51%.

At the end of March 2020, the app had just 8.6 million users, the S-1 filing showed, meaning the customer base more than doubled in a year.

The increase in users over the past year, and notably in the first three months of 2021, came as retail investors made their presence known in the markets by causing massive share-price rallies in meme stocks like GameStop and AMC Entertainment.

Robinhood came into the spotlight amid GameStop's epic rally in January when it halted buying of the stock, only allowing users to sell. Outraged traders flooded the app with one-star reviews on Google, lowering its user rating. Many said they would stop using the app in protest, and Redditors on investing thread Wall Street Bets called for legal action.

The company declined to comment. In its filing, the company said Robinhood reached the top spot on the Apple App Store multiple times in the first quarter this year, and added that based on an internal brand study, more than half of 18 to 44 year olds know about Robinhood, a sign of the company's relevance.

Robinhood was launched in 2013 with the mission to "democratize finance for all." On Thursday, it publicly filed its IPO documents with the Securities and Exchange Commission with plans to be listed on the Nasdaq under the ticker "HOOD."