Monero is different. To mine Monero, you have to calculate hashes with an algorithm called Cryptonight. This algorithm is very compute heavy and – while overall pretty slow – was designed to run well on consumer CPUs.
There are solutions to run the Cryptonight algorithm on a GPU instead, but the benefit is about 2x, not 10000x like for other algorithms used by Bitcoin or Ethereum. This makes Cryptonight a nice target for JavaScript and the Browser.
Our miner uses WebAssembly and runs with about 65% of the performance of a native Miner.
Youtube does transcode to H.264 (which is the format which requires licensing, x264 is an open source encoder that outputs H.264 encoded video). There are a variety of chrome extensions and similar which will allow you to select H.264 on the majority of Youtube videos if you so choose, much of youtube's content is available in h264 as well as other formats.
Second, the reason that they default to VP9 is because it is a better low-bandwidth experience. It's certainly a tradeoff against power usage with H.264 since hardware acceleration for H.264 decoding is often available, but it is a calculated tradeoff based on the fact that people want their videos to load faster and in higher quality. You can read a little bit more about that here. https://youtube-eng.googleblog.com/2015/04/vp9-faster-better...
p.s. did checked coin-hive.com and hash rate is really poor - 24h/s on a 4 core machine is truly nothing compared to modern hardware miners.
Six years ago:
https://news.ycombinator.com/item?id=2566365
Additionally, does this automatically hook in to slush's pool or something? Bitcoin mining is practically useless on CPU; even the fastest CPUs out get way, way less than 10mhash. The average length of time to find a block at 9999khash and current difficulty is 1200+ days, so even that estimate is over-optimistic, so this isn't worth anything if your users don't sit on your site for 5 years+, unless it's hooked into a pool or some other contraption to pay on shares instead of blocks.
It hasn't gotten better.