Updated: August 14, 2025
There are four types of Page Load. Although the functions are similar, the order is different.Regardless of when the Launch library finishes loading, all the rules are guaranteed to be executed and they will be executed in the following order: Library Loaded (Page Top)>Page Bottom>DOM Ready>Window Loaded.
DOM Ready
When it fires:
- Once the DOM tree is fully built and ready to be accessed (DOMContentLoaded event).
- Images and other resources may still load afterward.
Best for:
- Most analytics page view tracking (e.g., Adobe Analytics s.t() call).
- Safely reading DOM elements.
Advantages:
- Reliable timing for tracking without waiting for all assets.
Library Loaded (Page Top)
When it fires:
- Immediately when the Adobe Launch library loads, at the very top of the page.
- Happens before HTML parsing finishes.
Best for:
- Setting variables early.
- Scripts that must run before the page renders.
Caution:
- No DOM access yet.
- Can block rendering if heavy code is used.
Page Bottom
When it fires:
- When the HTML document has been parsed to the end (</body>).
- Happens before external resources (images, CSS, etc.) finish loading.
Best for:
- Running code after all HTML elements are available but before the full page load event.
- A middle ground between Library Loaded and DOM Ready.
Caution:
- While HTML is complete, some scripts and styles may not yet be ready.
- Not as universally used as DOM Ready because DOM Ready is more standard in JS execution timing.
Window Loaded
When it fires:
- After the entire page is loaded, including images, CSS, scripts, and iframes.
Best for:
- Tags that depend on every asset being available (e.g., performance metrics, image-dependent widgets).
Caution:
- Slowest to fire — analytics events here might miss users who leave quickly.
Summary Table
Event Type | Fires When | Best For | Not Recommended For |
---|---|---|---|
Library Loaded | Launch library executes at page top | Early variable setup, critical scripts | DOM access |
Page Bottom | HTML fully parsed, before all resources | Code needing all HTML elements early | Asset-heavy code |
DOM Ready | DOM built and ready (DOMContentLoaded) | Page view tracking, DOM-based scripts | Asset-dependent tags |
Window Loaded | All assets loaded (load event) | Resource-dependent code | Fast analytics tracking |