Locus

Locus does one thing well: replace keyword-based find-in-page with semantic search. If you've ever spent minutes scrolling through a 50-page PDF looking for a specific concept whose phrasing you can't recall, Locus solves that pain instantly. It's browser-based, lightweight, and respects your privacy (no data leaves your machine for indexing). The free tier is surprisingly usable – 3 documents per day with AI summaries is enough for a daily newspaper habit or a couple of research papers. Professional at $9/month is reasonable for power users, especially with model choice and unlimited documents. The bring-your-own-key option for GPT-4o is a nice touch for those already paying for OpenAI. Where Locus falls short is scope. It's not a note-taking app, knowledge base, or research manager – it strictly helps you find and understand content you're already viewing. If you need to organize, cross-reference, or store information long-term, you'll need another tool. Also, there's no evidence of multilingual support, so non-English content may not work reliably. Compared to something like Memex or Hypothesis, Locus is simpler and more focused on search than annotation. It's best viewed as a CTRL+F replacement, not a full research ecosystem. If you're a student ploughing through dense textbooks, an analyst scanning morning news, or a researcher reviewing PDFs, Locus will save you time. If you rarely read long-form content, skip it.