Organise a personal wiki with nested notes, links, attachments and searchable reference material.
Free open-source desktop app · no feature paywalls · optional server uses your own resources

Notes, tasks & docs
Keep searchable notes, attachments and notebooks locally, with optional encrypted sync.
Keep searchable notes, attachments and notebooks locally, with optional encrypted sync.
Replace personal notes, linked reference material and a small personal knowledge base. Not a replacement for Notion relational databases, automations or real-time team collaboration. Obsidian itself is already free; this is an optional different notes workflow, not a claim that its base app requires payment. Open-source markdown note-taking and to-do application with end-to-end encryption syncing across all desktop and mobile devices for free.
Joplin Cloud is paid and optional. Dropbox/OneDrive sync uses your own account and its storage allowance; a self-hosted sync server costs hardware, hosting and backups. No paid API is needed for ordinary notes. No Notion-style relational databases or multiplayer editing; notes live in an app database rather than a directly editable Markdown vault.
Each comparison covers the workflow described above, rather than every paid feature.