Liner
AI search companion and web highlighter that delivers cited AI summaries alongside search results - trusted by 7M+ students and researchers worldwide.
Liner is an AI-powered research tool that overlays cited AI summaries directly on Google, YouTube, and news search results, letting users evaluate sources faster without opening every link. Its web highlighter lets users save and annotate any webpage or PDF with color-coded highlights that sync across devices. The AI assistant, trained on highlighted content, answers questions and summarizes across saved sources, creating a personalized research layer. Liner launched as a web highlighter in 2015 and added AI search features in 2022, growing to 7M+ users. It primarily serves students, journalists, and knowledge workers who need to research and synthesize information across multiple sources quickly.
Key Features
- AI summaries with citations displayed directly alongside Google, YouTube, and news search results
- Web highlighter - highlight and annotate any webpage or PDF with color-coded marks that sync across devices
- AI assistant trained on your personal highlights - ask questions across saved research in natural language
- Multi-source research synthesis - generate summaries across all highlighted content on a topic at once
- PDF and paper reader with AI explanation, definition lookup, and inline annotation tools
- Chrome extension and mobile app for capturing highlights from any device or browser context
Use Cases
- Students conducting research by capturing and synthesizing highlights from multiple papers and articles
- Journalists fact-checking and sourcing stories by saving annotated web sources in a searchable library
- Knowledge workers building a curated research library with AI-assisted summarization across saved content
- Academics reviewing literature by highlighting PDFs and asking the AI to synthesize findings across them
Pros
- 7M+ user base makes Liner one of the most widely used AI research companions in the student market
- AI summaries appear directly on search results pages - no additional clicks to evaluate source relevance
- Highlight-based AI training means answers are grounded in your personal curated sources, not generic web data
Cons
- AI summary quality varies significantly on highly technical or niche topics outside mainstream sources
- Free tier limits highlight syncing and AI queries - heavy researchers hit the cap quickly
- Highlights are saved in Liner's ecosystem - no native export to standard note-taking tools like Notion or Obsidian
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