Glasp

Glasp is a free Firefox browser extension that unifies web, PDF, YouTube, image, and Kindle highlighting with AI summarization and a social discovery layer. Its product strength comes from combining annotation, AI models, and community-curated content into one workflow. The supplied listing shows a narrow visible social-proof footprint with only three reviews and no public pricing, revenue, team, or growth data. As a business, it sits in a crowded market with strong competitors; the likely value is not the basic highlighter but the social knowledge graph and AI-assisted research workflows that can be built on top. A direct broad clone is unattractive, but the product logic offers useful directions for a niche founder.