We're only a little over a month into the new year, and some stocks are already starting to separate themselves from the pack. Today, let's examine two growth stocks that have come quickly out of the gates in 2025: Duolingo (DUOL 1.14%) and Spotify Technology (SPOT -0.46%).

Here's why I think they are stocks worth buying and holding for the long term.

Image source: Getty Images.

Duolingo

First, let's have a look at Duolingo.

Here's the thing I love about Duolingo: It's the perfect reason to quote perhaps my favorite investing hero: Peter Lynch. Lynch said, "Buy what you know." And in the case of Duolingo, I've followed his advice.

The company operates an online-learning platform and app. I love using it to study foreign languages, along with many of my friends and family. That's what got me interested in the company and its stock.

However, what sets Duolingo apart is how innovative it is. The company hasn't been content with just teaching its users foreign languages. It has branched out into music education, math education, and, crucially, it seems to be a prime mover in embracing generative AI.

The company uses generative AI to develop and refine its personalized lesson plans. Its app fine-tunes the experience for each user, ensuring that individual strengths and weaknesses are covered to promote maximum learning and retention.

What's more, the company has unveiled other AI-powered interactions, like Video Call. Within Duolingo Max, the company's top subscriber tier, a well-known Duolingo character "calls" users periodically, then engages in a real-time conversation, simulating a tutor-like experience on the go.

Going forward, Duolingo will need to continue growing. According to consensus estimates compiled by Yahoo Finance, the company should generate $744 million in revenue in 2025, up almost 30% year over year.

If the company can match -- or even exceed -- those estimates, Duolingo will go a long way to proving its business model is thriving. And that makes it a stock I want to own for years to come.

Spotify Technology

Next, let's examine Spotify Technology.

Let me cut to the chase: There are good stocks, and there are great stocks. And, in my view, Spotify has made the transition from good to great. Here's why.

Back in 2022, Spotify was feeling the pain. The company was unprofitable despite its massive user base. In turn, CEO Daniel Ek made difficult decisions; he cut costs by trimming Spotify's workforce and refocusing the business on music streaming.

Ek's decisions have paid off. As of this writing, Spotify shares have advanced by more than 670% since the start of 2023. That means if you had invested $10,000 on Jan. 2, 2023, you'd have over $77,700 today.

At any rate, Spotify doesn't appear to be slowing down anytime soon. The company recently announced another fantastic quarter (for the three months ending on Dec. 31, 2024).

Among the highlights, the company announced year-over-year revenue growth of 16%, bringing full-year 2024 revenue to 15.7 million euros ($16.30 million). Meanwhile, gross margin hit an all-time high of 32.2%, and free cash flow reached 877 million euros ($910.59 million). Both figures represent all-time highs in their respective categories.

In short, Spotify is running at full steam. Investors would be wise to consider the stock for the long term.