SAN FRANCISCO (AP) — Netflix's video-streaming service has been thriving for so long that other companies are striving to duplicate its success in other kinds of digital entertainment and content.

Spotify's music-streaming service has emerged as the most celebrated of the aspiring clones, despite significant challenges that will make it difficult to keep growing at the same pace as Netflix has been in video streaming.

Netflix's first-quarter earnings released Monday served as the latest reminder why its business model will be a tough act to duplicate for any copycat. The company added 7.4 million subscribers during the first three months of the year, ending March with 125 million worldwide. The performance surpassed analyst projections, helping to lift Netflix's stock by 7 percent in extended trading.