Reversing YouTube’s “Most Replayed” Graph
Hi HN, I recently noticed a recurring visual artifact in the "Most Replayed" heatmap on the YouTube player. The highest peaks were always surrounded by two dips. I got curious about why they were there, so I decided to reverse engineer the feature to find out. This post documents the deep dive. It starts with a system design recreation, reverse engineering the rendering code, and ends with the mathematics. This is also my first attempt at writing an interactive article. I would love to hear your thoughts on the investigation and the format.
In plain words
This article investigates YouTube's "Most Replayed" feature by reverse engineering the visual artifacts that appear in its heatmap graph. The author explores the system design, rendering code, and underlying mathematics behind the recurring dips that surround peak replay moments. It is aimed at developers and technically curious people interested in understanding how YouTube's features work. The piece is presented as an interactive article format, combining technical analysis with explanatory visualizations.
written from the facts on this page · September 2026
More dev tools this month
the category →
Open-source GTM skills for technical founders
Dev tools · 29d ago · gtmcofounder.com
OpenTrailPaper is open-source bike computer firmware for the LilyGO T5S3 4.7" E-Paper PRO. It supports offline maps, GPX routes, FIT recording and Bluetooth sensors.
Dev tools · 2d ago · opentrailpaper.com
Launched alongside, January 2026
the whole month →- IN
Hey HN! I wanted to share something I built over the last few weeks: isometric.nyc is a massive isometric pixel art map of NYC, built with nano banana and coding agents. I didn't write a single line of code. Of course no-code doesn't mean no-engineering. This project took a lot more manual labor than I'd hoped! I wrote a deep dive on the workflow and some thoughts about the future of AI coding and creativity: http://cannoneyed.com/projects/isometric-nyc
AI · Jan 2026 · cannoneyed.com
Automatic AI-powered code reviews the moment you open a PR
Dev tools · Jan 2026 · kilo.ai
