seendiff is an open-source, local-first code diff viewer that tracks review progress and enables AI-driven walkthroughs for large git repositories.
What the product does and how it is positioned
seendiff is a specialized tool designed for reviewing large code changes within git repositories. It functions by launching a local server that renders a diff interface in the user's web browser, focusing on progress management and performance.
The tool is built to assist both human reviewers and AI coding agents. It automates the tracking of viewed code and provides manual controls to mark sections as reviewed, so that progress is maintained even if the underlying commits are modified or the session is interrupted.
Source-supported ways to use the product
Reviewers can manage massive diffs with up to 40,000 lines per file while tracking exactly which sections have been seen and reviewed over multiple days.
Users can integrate coding agents to generate step-by-step walkthroughs of complex changes, making it easier to understand the logic behind automated code generation.
The documented workflow, where available
Install the tool using pip or the uv package manager on a system with Python 3.10+ and git.
Navigate to a git repository in the terminal and execute the command to start the local server and open the browser interface.
Scroll through the diff to automatically mark sections as seen, and use keyboard shortcuts to mark blocks or entire files as reviewed.
Optionally prompt a coding agent to install the walkthrough skill to receive explanations of the diff directly within the interface.
A core function of the tool is its ability to maintain the state of a review across various git operations. Unlike standard diff tools where progress is lost upon closing the application, this tool saves the 'seen' and 'reviewed' status of specific code blocks.
This persistence is designed to survive common development workflows such as rebasing or amending commits. This allows a reviewer to start a task, perform local repository maintenance, and return to the exact point where they left off without re-evaluating previously cleared code.
Checks to run with your own material and workflow
What was checked and when
Answers based on the source-checked product record
The tool automatically marks code blocks as 'seen' as soon as they are scrolled into the user's viewport within the browser interface.
No, the tool operates entirely on a localhost server and does not require an internet connection or external account to function.
Yes, it is designed with virtualization technology to ensure that files as large as 40,000 lines can be scrolled and reviewed smoothly.
The tool is designed so that review progress survives common git actions like rebasing, amending commits, or closing the application window.
Reviewers can ask their coding agent to install a specific skill that enables it to write and display step-by-step walkthroughs of the code changes.
