As a FIDE Master, I hated my opening prep. So I built a free tool to fix it.

Hello Lichess community!
I’m a FIDE Master and a solo developer. Throughout my chess career, opening preparation has always been the most frustrating part of the game. You spend hours clicking through lines in ChessBase, you think you know the theory, and then you play a Blitz session on Lichess and immediately forget your prep on move 7.
Worse yet, finding out exactly where you deviated from your own files usually requires manually checking every single game.
I wanted a tool that would automatically look at my actual Lichess games, compare them to my repertoire, and show me the "holes". Since I couldn't find a perfect tool for this, I spent the last few months building one.
It’s called Forkline, and I want to share it with you all today. It is 100% free, has no ads, and uses Lichess OAuth so you don't even need to create a new password.
Here are the 4 core modules that make up the app:

1. 🏗️ Repertoire Builder

This is where you build and manage your opening trees. It integrates directly with the Lichess Masters database. Plus, it runs Stockfish 18 locally in your browser via WebAssembly. You get instant, powerful engine evaluations without any network lag.

2. 🕵️ Gap Analysis

You connect your Lichess account and select your repertoire. Forkline bulk-scans your recent games and finds the exact moments where you (or your opponent) deviated from your theory. Instead of guessing why you lost out of the opening, you instantly see your "Gaps" and can add them to your files.

3. 🔍 Game Inspector

When you need to look closer at a specific game, the Game Inspector comes in. It allows you to deeply analyze an individual game move-by-move alongside your repertoire tree, making it easy to pinpoint exactly where your preparation ended and where the critical mistakes happened.

4. 🧠 FSRS Trainer

Spaced repetition is the only reliable way to remember deep prep. Forkline's Trainer uses the modern FSRS (Free Spaced Repetition Scheduler) algorithm. It’s significantly more efficient at scheduling reviews, turning your repertoire and your patched "Gaps" into smart flashcards.

Looking for Beta Testers

Right now, Forkline is in early Alpha and hosted on a starter server. I am looking for chess players of all levels to try it out, give me honest feedback, and help me catch bugs.
Link to the app: https://forkline.online/
Discord for feedback/bugs: https://discord.gg/DZCtYWGdj
A quick warning: Because it’s an early build, things might break if too many people hit "Analyze" at the exact same time. If you encounter a bug or the server slows down, please let me know in the Discord!
I’d love to hear your thoughts. May your pieces always find the right squares!