Label Studio

Label Studio is the open-source standard for data annotation, covering images, video, audio, text, and time series under one configurable interface. Labeling configs, written in a compact XML-like syntax, define exactly what annotators see and produce, from bounding boxes and polygons to named entities and audio regions.

An ML backend hooks your own model into the loop for pre-labeling, so humans correct suggestions instead of starting from scratch. Exports cover standard formats including COCO, YOLO, and plain JSON, and a Python SDK plus REST API drive programmatic project management.

The Community edition is free to self-host under an open license, which is why teams with sensitive data or custom pipelines standardize on it. The interface is less polished than commercial tools, enterprise features such as SSO, RBAC, and analytics are paid, and self-hosting means you own upgrades and scaling.