The new definition uses two different embed URLs as some documents can only be embedded with one or the other.
When visiting the last post of a thread, dynamically-sized embeds (such as tweets) from previous posts will expand upward even if they fully appear on the screen. It will keep the post the user is reading at the same position on the screen and prevent the useful content from moving around as the result of other elements loading.

A bug has been fixed that caused the lazy loader to incorrectly determine which way the page was being scrolled. It didn't really have any impact on the user experience and is only mentioned for completeness.

At this point I'm happy with the behaviour of the lazy loader and I don't have any more changes planned. The lazy loader is meant to be almost invisible so I may write a full description of the multiple ways it improves the user experience behind the scenes.
The following sites have been updated: Facebook, Gist, Google+, Imgur, Instagram, Pinterest, Reddit, Telegram, Tumblr, and Twitter.

The lazy loader doesn't wait anymore for the page to be fully loaded if it's taking too long. It helps in threads that contain large GIF images.
Added support for /i/ URLs in Twitter.
Updated lazy loader to detect iframes hidden in quotes.
The option is off by default. You can turn it on if you have a dark style and Facebook posts are unreadable.
This update should provide a slightly smoother experience with dynamically-sized content (e.g. tweets) across browsers.
The lazy loader update should provide a smoother experience when loading up multiple tweets on a page.

It also fixes an issue with Google Chrome's back/forward navigation, which could incorrectly load the same embeds twice or prevent them from being correctly resized.

Please report any regressions or issues related to dynamic content such as tweets and Instagram posts.
This update contains a few changes and improvements. If all goes well, you won't notice any of them.
  • Gfycat, Instagram and Twitter have been updated.
  • An error message is now displayed if a media site template is missing.
  • The lazy loader has been updated to improve its efficiency slightly and reduce jank when loading dynamically-sized iframes such as Twitter's.
  • A short CSS transition has been added to resize dynamic iframes more smoothly.
  • Several add-on options have been added:
    • Whether to display the add-on's branding as a small link at the bottom of the page. (default: on)
    • Whether to use YouTube's enhanced privacy mode. (default: off)
    • Whether to use the new Instagram and Twitter embeds. (default: on) If you've ever had any issues with tweets being cut-off, it may help with that.
Updated Google Sheets, Hudl and MSNBC