Margin Call is a Chrome extension designed to enhance the experience of reviewing pull requests (PRs) on GitHub by allowing users to comment on rendered markdown previews. This tool addresses a significant limitation in GitHub's functionality, where users can only leave inline comments on code but not on the rendered markdown previews. With Margin Call, users can seamlessly interact with documents such as technical requirements documents (TRDs), request for comments (RFCs), architecture documents, and changelogs directly within the markdown preview interface.

The extension bridges the gap between code comments and markdown reviews, eliminating the need to switch back and forth between the rendered output and the raw markdown. This streamlined process improves productivity and facilitates clearer communication among team members during the review process. Margin Call is a free tool that falls under the category of add-ons and tools for Chrome browsers, making it accessible for developers looking to optimize their workflow on GitHub.