Loki vs Visual Regression Tracker

Loki is a free, MIT-licensed tool for checking Storybook projects for visual regressions. It captures story screenshots and compares them with reference images, producing visual differences for review. The workflow is to create reference screenshots, run comparisons, review the differences, and approve updated references. Loki is designed for continuous integration, where tests can fail if reference images are missing. Capture targets include Chrome in Docker or locally, Chrome in AWS Lambda, the iOS simulator, and the Android emulator; an AWS Lambda renderer is available for large test suites. Node 16 or later is required. Recent Storybook versions need no extra integration for non-React Native projects, while React Native setup uses an import in `storybook/storybook.js`. Projects can configure Loki in a `package.json` section or supported Loki configuration files. Loki does not start Storybook or simulator and emulator servers, so they need to be running before tests. Documented animation limitations include looping requestAnimationFrame animations, GIFs, SVG animations, native Lottie animations, and React Native Animated.

Visual Regression Tracker compares submitted screenshots with accepted baselines to flag unexpected visual changes. It keeps baseline history and lets teams exclude image regions from comparisons. Projects can choose among Pixelmatch, Looks-Same, Odiff, and a VLM comparison provider. The review dashboard supports side-by-side, diff, scrubber, and onion-skin views, with one-click approval. Feature branches inherit the main branch baseline until a change is approved, and builds can post commit status to GitHub or GitLab. The project lists agents for Playwright, Cypress, CodeceptJS, and Robot Framework, plus JavaScript, Java, Python, and .NET SDKs; its REST API supports other languages. A standalone JAR can compare PDFs as well as images. Deployment is self-hosted using Docker images, and the project says this keeps data inside the user's intranet. The documented screenshot upload payload limit is 20 MB. Each project has one owner; members can view snapshots and approve changes, while some actions are owner-only. It is open source under Apache-2.0.