Slack Technologies Inc., a provider of chat services for businesses, is preparing for an initial public offering in the first half of 2019, the Wall Street Journal reported on Friday, citing people familiar with the company's plans.

The San Francisco-based startup expects it could achieve a valuation well in excess of about $7 billion, the level at which a recent round of financing valued the company, the WSJ report said.

The startup competes with Microsoft's Teams, Alphabet Inc's Google Hangouts, Cisco Systems Inc.'s Webex Teams, Workplace by Facebook Inc. and others in the workplace collaboration market, which research firm IDC projects will be worth $3.2 billion by 2021.

Slack, which counts Softbank among its top investors, has more than 8 million daily active users and 3 million paid users, it said earlier this year.

The company has not hired underwriters yet but could do so soon, according to the report.