Top alternatives for Diigo
Weava
Weava is a workspace for research where you can highlight, organize and collaborate your research materials.
I really like Weave, I used to use Liner, and I gotta say Weave is far more complete with lots of extra features.
Still on the free plan, but…
See moreSpade Chrome Extension
We believe everyone deserves freedom on the web. With Spade, you can connect inspiration, ideas, and information with annotations on any site, and even share them with others. Understand the web better with site analytics, vocab, and summarization.