Every platform has one signal

There is no universal “engagement.” Each platform’s algorithm rewards a different primary signal, and the rest is mostly noise relative to that signal:

• YouTube — watch time and retention.
• TikTok — completion rate.
• Instagram — saves and Reels engagement velocity.
• LinkedIn — native, long-form authority.
• X — recency and conversation.

Optimize for the wrong one and you can work hard, move a number, and gain nothing — because you moved the number the platform wasn’t grading.

The implication is uncomfortable for anyone selling a single “growth score”: a good system has to key off each platform’s own signal, not flatten everything into one blended vanity number. That flattening is exactly where most tools quietly fail you.