Annotation GitHub Repositories (2026) · Open Source Tools

Code as configuration. Annotate a Java entity with @Erupt and ship a production-grade admin backend in minutes — UI, RBAC, audit logs and APIs, all generated at runtime. No codegen, no frontend.

Annotate Markdown in the terminal: select, comment, looks-good, delete; send the review to your agent.

CVAT is a leading data annotation platform for image, video, audio, and 3D datasets. It offers open-source, cloud, and enterprise products, as well as labeling services, with AI-assisted labeling, quality assurance, team collaboration, analytics, and developer APIs.

a library for audio and music analysis

Label Studio is a multi-type data labeling and annotation tool with standardized output format

Free, open-source screenshot tool, screen recorder, and video editor for Mac. Auto-zoom, smooth cursor, captions, OCR, scrolling capture, and annotations. Native, private, no account.

📝 Annotation tool for macOS

Annotate terminal text, review documents and agent replies in Herdr, and send the feedback straight back to the agent.

🚀 A coroutine framework that focuses on hyperspeed and flexibility. Building microservice or middleware with ease.

⌘⌘ - A lightweight, native macOS screenshot tool that lives in your menu bar. Double-tap ⌘ Command to capture any region of your screen — instantly copied to clipboard, or annotate first with pen and mosaic tools.

IntelliJ IDEA / PhpStorm Symfony Plugin

potato: the portable annotation tool

Add image annotation functionality to any web page with a few lines of JavaScript.

Agent skill: outline, mask and count objects in photos with Meta's SAM 3 on your own NVIDIA GPU, with review, exports and a viewer. Works with Claude Code, Codex, Cursor, Pi and other Agent Skills clients.

Native, local-first macOS screenshot, annotation, and pinboard tool.

Human-feedback and data-governance infrastructure for RSI research: annotation, review, provenance and frozen dataset candidates.

Screenshots, markup and screen recording for macOS and Windows, in Rust. Under 1.5 MB, and idles at about 12 MB of memory.

Free, open-source screenshot and screen recording app for macOS: capture, annotate, add backgrounds, and record MP4 or GIF. A native CleanShot X alternative.

Your new favorite, free, and open source screenshot tool