Lyft is aiming to debut in March or April, according to people familiar with the matter. By filing with the Securities and Exchange Commission now, the company should have enough time to answer questions from the agency and keep to its schedule.

Lyft, which is much smaller than Uber, is widely expected to beat its ride-hailing rival to a listing, and in doing so would afford public investors their first opportunity to buy into the fast-growing industry.

The IPO will be a test of how such investors value the industry’s players. Uber, Lyft and a host of other ride-hailing firms have received vast amounts of money from private investors at high valuations but still need a lot more capital as they continue to generate big losses.

After a blockbuster year for IPOs, 2019 could present a strong encore, with big names like Lyft, Uber, Slack Technologies Inc. and potentially Airbnb Inc. and Palantir Technologies Inc. making debuts. Recent whipsaws in the stock market might prompt some companies to go public sooner than expected to beat a possible further downturn. But if one comes quickly, it could also force companies to shelve their plans.

In October, The Wall Street Journal reported that Lyft had picked underwriters for its offering. The firm’s valuation is expected to top the $15.1 billion it was valued at earlier this year.

Meanwhile, Uber, has received proposals from bankers that value it as high as $120 billion, the Journal reported. Companies often consider such proposals before hiring IPO underwriters.

Uber Chief Executive Dara Khosrowshahi has said the company would aim to go public in the second half of 2019. But the IPO could come sooner, as Uber looks to tap a robust market for public offerings.

Uber’s pitch to investors will likely seek to distinguish the company from Lyft by emphasizing its global reach and the platform nature of the business, according to people familiar with the matter. Mr. Khosrowshahi has pointed to the Uber Eats food-delivery service as a prime example of how Uber can use its existing network to rapidly build up ancillary businesses.

By contrast, Lyft is expected to point out that its business, which operates mostly in the U.S. and Canada, doesn’t have the same giant losses as Uber, people familiar with the matter said.

Like Uber, Lyft makes money by taking a commission on rides booked through its app. It posted third-quarter revenue of $563 million, up 88% compared with the year-earlier period, the Journal has reported. It lost $254 million in the latest quarter.

In November, Uber said its third-quarter revenue rose 38% to $2.95 billion, and it posted a loss of $1.07 billion.

Uber has weathered a series of scandals, including claims of workplace sexual harassment and the alleged theft of trade secrets from rival Alphabet Inc. Mr. Khosrowshahi has sought to win back investors, drivers and riders amid growing competition.

Green Light

Lyft's timeline appears to be slightly ahead of Uber's as both companies push to go public.

Valuation

$76 billion

$15.1B

Employees

20,000

Worldwide

4,500

Funds raised

$20 billion

Includes debt

$5.1 B

Market share*

69%

28%

Other: 2%

3Q results

$563 M

Revenue

$2.95 billion

Loss

$1.07 billion

$254 M

*Percentage of sales within the U.S. ride-sharing market

Sources: the companies; Second Measure (market share)

Lyft has competed with fiercely with Uber, but only in the U.S. until recently. It expanded to Toronto late last year and has indicated it will offer ride-hailing services more broadly across Canada. It has also explored expanding into Western Europe, according to people familiar with the matter.

Uber is available in nearly 70 countries world-wide and enjoys a considerable market-share lead in the U.S. According to Second Measure, which tracks credit-card spending data, Uber had 69% of the market, compared with 28% for Lyft as of October. Lyft peaked at 29% in August.

—Greg Bensinger contributed to this article.

Write to Maureen Farrell at maureen.farrell@wsj.com and Micah Maidenberg at micah.maidenberg@wsj.com