Perplexity
Perplexity AIAnswer engine that cites its sources for every claim
Reading, sourcing and working through papers.
7 tools
Answer engine that cites its sources for every claim
Research notebook grounded strictly in the sources you upload
Free academic search with citation context and paper summaries
Systematic literature review across a large database of papers
Search engine that answers questions from peer-reviewed findings
Reads and explains research papers, with literature review tools
Visual citation mapping for discovering related papers
Tools in this category overlap more than their marketing suggests. The useful difference is usually not the model behind them but what they let you do around it: how much control you get over the output, how the work is organised once you have it, and whether the free level is enough for what you are doing.
Each page below lists what the tool is good at and what it is not, along with alternatives worth comparing before you commit.