Robinhood Markets and TD Ameritrade said they resolved trading and other technical problems that were part of wider industry glitches Monday.
Robinhood had problems related to equities, options and cryptocurrency trading in the morning and said shortly after noon in New York that the issues were fixed. TD Ameritrade said in a statement that clients had experienced high levels of slowness on its web platform and mobile app. Both companies apologized.
Charles Schwab and Vanguard Group also said they were working to resolve issues with their websites, among other disruptions. Thousands of customers lodged complaints on Downdetector.
Speculation online focused on whether some of the problems were related to the Apple and Tesla stock splits effective Monday.
Self-guided traders stuck at home during the COVID-19 pandemic have helped give online brokers a boost this year. Second-quarter retail U.S. equity trading volume surged more than 50% from the preceding three-month period, according to Larry Tabb, head of market structure research for Bloomberg Intelligence.
While online brokerages routinely experience brief outages, it's rarer for several of them to happen simultaneously. Downdetector listed more than 2,900 problems for Robinhood and more than 7,000 for Ameritrade.
Judy Burns, an SEC spokeswoman, declined to comment, and a spokesman for the Financial Industry Regulatory Authority didn't immediately respond to a request for comment.
Robinhood, which has helped lead the gains in online trading this year, is the subject of an investigation by regulators into its handling of an outage in March.
It wasn't immediately clear whether Monday's disruptions are related. Schwab said in a statement that its website may be intermittently inaccessible for some clients. Vanguard was experiencing "intermittent connectivity issues impacting our websites and phones," a spokeswoman said.