Matan · Performance · Loading
Total Blocking Time (Performance)
TBT is the lab proxy for INP: how long the main thread was blocked during load.
Pass condition in our engine: Lab TBT is under 200ms when measured.
This Performance check is part of SEO-GEO scoring 2.2.1, last updated 2026-09-18. About 90 percent of the evaluation runs on the HTML we crawl, so you can verify the same pass condition with a free report.
1. Problem description
Long tasks over 50ms make taps feel dead. Good TBT is under 200ms.
2. Most common causes
- Huge bundles parsed on the main thread.
- Third-party tags (chat, ads, A/B tests).
- Hydration of a large client-side app.
3. How to fix it
- Code-split and defer non-critical JS.
- Load third parties after first interaction.
- Break long tasks with scheduler.yield().
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