I’m spending a lot of time debating people about Bitcoin online these days. One issue that I encounter regularly is that my opposite colloquists are unaware of the contributions the Blockstream developers have added to the Bitcoin project since the company was founded. 

My aim is twofold: I’d like to be able to simply link this question next time I read "Blockstream produces only vapour, and contributes nothing", and I think that the answer to this question deserves more visibility.

**Please list what measurable contributions Blockstream developers have made to the Bitcoin project?**