But take a closer look at the tech start-ups to hit the public markets this year, and it quickly becomes apparent that the struggles of Uber and Lyft have much more to do with their financial performance and less to do with the market. Investors’ demand to own a piece of fast-growing young technology firms remains robust, and nearly halfway through the year, 2019 is shaping up to be among the strongest years for tech companies to go public.

So far, 25 tech companies have raised $19 billion through initial public offerings on United States exchanges, according to the data provider Dealogic. Over all, those stocks have gained 34 percent on their first day of trading, the best performance since 2013, and, on average are up 30 percent.

On Thursday, Slack became the latest unicorn to see its shares soar on their first day of trading. The messaging and workplace collaboration company eschewed the more common I.P.O. process and went public through a direct listing, in which a company does not issue new shares or raise additional capital. Its stock rose about 50 percent from a reference price of $26.

Slack’s debut came just a week after CrowdStrike, a cybersecurity firm; Chewy, an online pet-supply retailer; and Fiverr International, a freelance-services marketplace, all went public and gained more than 50 percent on their first day of trading.

After years of waiting, stock market investors finally have an opportunity to own shares of Silicon Valley’s most valuable companies. The start-ups that have also made their public market debuts this year include Pinterest, Zoom Video, Beyond Meat and PagerDuty. Airbnb, WeWork, Palantir, The RealReal, and the food-delivery service Postmates are expected to follow later this year or early next year.