They post it on their webpage.
25% based on volatility
25% based on market momentum/volume
15% based on social media
15% based on surveys
10% based on coin market cap dominance
10% based on Google search trends
This is an interesting metric that I will be adding to my webpage and keeping a closer eye on.
Actually traditional markets like the DOW and NASDAQ has their fear and greed index taken from almost the same metrics. But this doesn't help in predicting the price action especially if you are margin trading. Maybe best for long holds, knowing when to sell is usually when the sentiment reaches extreme euphoria.