ideally qualified to help them learn. The result is an exceptional experience for Learners. We use AI to select the ideal Expert for a given Learner’s needs, taking into account approximately 100 variables, including Learner and Expert attributes, diagnostic assessments, and data from past learning experiences. We believe quality matching is a key differentiator for Nerdy, something that legacy offline models and online directories struggle to do well.
Nerdy’s multi-format online learning destination improves access and lowers cost barriers to high-quality, live learning and other additive learning resources. Our product suite includes paid
instruction and small group class products, in addition to free live large-format online classes that are interactive and can accommodate 500 to 50,000+ Learners, including classes taught by celebrity scientists, astronauts, and wildlife experts. Additionally, Nerdy’s library of hundreds of thousands of resources, including online adaptive diagnostic tests and practice problems, are offered completely free for Learners. Our free content helps attract new users to our platform and complements our paid product offerings by increasing retention of our existing users.
Our platform and multiple learning formats allow us to deliver value in more ways and establish lasting relationships between Learners and Experts. This generates powerful network effects in our business: high customer satisfaction attracts more Learners to our platform, which in turn attracts more Experts as well. These dynamics have allowed us to deliver durable growth and healthy unit economics.
Active Learner growth is up 56% for the three months ended March 31, 2022 compared to the same period in 2021, while paid online sessions have grown 57% in the same time frame. For the year ended December 31, 2021, Active Learners increased by 46% from approximately 87 thousand in 2020 to approximately 127 thousand in 2021, while paid online sessions increased by 73% in the same time frame from 1,113 thousand to 1,921 thousand sessions. “Active Learners” is defined as the unique number of Learners attending a paid online
instruction, a paid online class, or a paid group tutoring session in a given period.
Revenue during the three months ended March 31, 2022 increased $12,360 thousand from $34,565 thousand to $46,925 million, or 36%, compared to the prior year period. We continue to innovate and bring new products to market to deepen relationships with Learners, further extend our ability to reach new audiences, such as Professional and Learning Differences, and introduce new products including Varsity Tutors for Schools, all while increasing engagement among our Experts to drive meaningful top line revenue growth. Revenue for the year ended December 31, 2021 increased $36,696 thousand from $103,968 thousand to $140,664 thousand, or 35%, compared to 2020. Online revenue increased by $43,224 thousand from $97,440 thousand in the year ended December 31, 2020 to $140,664 thousand in the year ended December 31, 2021, an increase of 44% year over year. We completed the transition to delivering live instruction 100% online in April 2020. We scaled and integrated several new services, including
instruction and small group classes, as well as free services including large format group classes, and adaptive self-study together into a single comprehensive learning destination. These initiatives drove revenue growth throughout the second half of 2020 which continued through 2021.
For the three months ended March 31, 2022, gross profit increased to $32,773 thousand from $23,373 thousand, or 40%, compared to the same period in 2021. Gross margin of 70% for three months ended March 31, 2022 was 220 basis points higher than gross margin of 68% for the three months ended March 31, 2021. Gross profit increases were driven by growth across consumer one-on-one audiences, growth in our small group class and tutoring formats, and the introduction of new products, including Varsity Tutors for Schools. For the year ended December 31, 2021, gross profit increased to $93,964 thousand from $69,134 thousand for the year ended December 31, 2020, and for the year ended December 31, 2021, gross margins increased to 66.8% from 66.5% for the year ended December 31, 2020. Gross profit expansion was driven by the adoption of
online learning, expansion across more subjects and more audiences (driven by professional and learning differences), and growth in our small group class format.
Our net loss for the three months ended March 31, 2022 was $31,747 thousand, compared to a net loss of $5,726 thousand for the three months ended March 31, 2021. Our net loss in the year ended December 31, 2021 was $30,679 thousand, compared to a net loss of $24,663 thousand in the year ended December 31, 2020.