Algorithm cheat sheets: what X, Instagram, YouTube and TikTok actually say they rank

# Algorithm cheat sheets: what X, Instagram, YouTube and TikTok actually say they rank

PaperChase research report, version 1.1 (Markdown edition). For creators, social managers, small agencies and founders who post for reach. Edition date: 2026-10-15. X weights read from the public source code on 2026-10-15. Instagram, YouTube and TikTok sections researched 2026-09-07; every source link was checked and resolved on 2026-10-15.

## How to read this report

Every claim carries one of three labels.

| Label | Meaning |
|---|---|
| **Published** | The platform said it in its own docs, blog, help center or public source code. Linked. |
| **Via secondary** | A trade outlet reported a platform statement we could not find as dated text on a platform-owned page. Treat with care. |
| **Lore** | Common creator advice with no matching platform source. Listed so you can stop paying attention to it. |

Two rules hold throughout:

1. **No invented numbers.** Instagram, YouTube and TikTok publish signals and rough order, not weights. This report never turns those into percentages or ratios.
2. **X is the exception.** X has published the source code for its For You ranking, including numeric weights. Those numbers are printed here with the commit they came from.

## Contents

1. X For You: the published weights and what they mean
2. Instagram: four surfaces, four sets of signals
3. YouTube: appeal, engagement, satisfaction
4. TikTok: For You factor groups and stated non-factors
5. Cross-platform playbook: what travels and what dies
6. Ethical tests you can run this month
7. Lore to stop believing
8. Sources