Last updated: May 2021 Table Of Contents Introduction How was it done before? How to use 3.1 Interlude: PerformanceTimeline 3.2 ResourceTiming 3.3 Initiator Types 3.4 What Resources are Included 3.5 Crawling IFRAMEs 3.6 Cached Resources 3.7 304 Not Modified 3.8 The ResourceTiming Buffer 3.9 Timing-Allow-Origin 3.10 Blocking Time 3.11 Content Sizes 3.12 Service Workers 3.13 Compressing ResourceTimi
![ResourceTiming in Practice](https://cdn-ak-scissors.b.st-hatena.com/image/square/30278a6d1fc13c5b4290c3561a5253720930187b/height=288;version=1;width=512/https%3A%2F%2Fo.nicj.net%2Fwp-content%2Fuploads%2F2015%2F05%2Fresource-timing.png)