Locus

Locus is an AI search tool. A Chrome extension that adds natural language search and AI summarization to web pages and PDFs. It summarizes sections, brainstorms further reading, builds study note cards and saves favorite answers. Free tier with a three document daily cap; Professional removes limits and adds newer models and an OpenAI key option.

Locus is a browser extension that replaces keyword hunting with natural language search across the documents and pages a reader already has open. Instead of guessing which exact phrase an author used and clicking through a long list of CTRL + F matches, a reader describes the passage they want ("the section on thermodynamic entropy") and Locus retrieves it. The extension works on both web pages and PDFs, which matters for people whose reading load lives in online textbooks, journal articles and dense reports. Beyond retrieval, Locus bundles a set of AI helpers aimed at comprehension and retention. It can summarize a full page or just a selected portion, brainstorm adjacent research topics and further reading, and generate note cards for studying. A Favorites feature stores answers and passages so a reader can return to them later rather than re-running the same query. The company positions the product for students and analysts, and its testimonials come from those two groups: an analyst skimming morning news, a research assistant working through lab papers, a student referring back into an online physics textbook. The free tier covers smart search, AI helpers, web pages and PDFs, plus saved favorites, with a daily cap of three documents. The Professional plan removes document limits and adds newer AI models, a role selector, faster processing and an OpenAI integration that can run on your own API key. Supported models listed on the site include OpenAI GPT-4o and 4o mini, GPT-3.5, Anthropic Claude 3 Haiku and Google Gemini 1.5 Flash, with updates promised within days of new releases. Monthly and annual billing differ in price and trial length. Locus sits in the same neighborhood as general chat assistants and PDF chat tools, but its angle is narrower: it works inside the browser on the material you are already reading, rather than requiring uploads or a separate chat window. That makes it a light commitment for readers who mainly want faster navigation and quick summaries, and a weaker fit for anyone needing deep document management or team collaboration.