We have updated the jQuery version that Stack Overflow and Stack Exchange use from version 1.7.1 to 1.12.4 today (Tuesday, September 27, 2016). jQuery is an infrastructure library, and we've been running on an old version for a while because it worked well. However, there are a few improvements and features that made it compelling for us to upgrade, especially since some parts of the site already used a different version.
As a user of our Q&A sites, nothing should visibly change, as this is an infrastructure rather than a feature update. However, with an infrastructure update like this, there is always a chance for things to slip through the cracks.
If you encounter functionality that used to work yesterday and is broken today, please leave an answer on this thread and accept my apologies in advance.
Please be aware of our browser support matrix.
Do note that userscripts that rely on deprecated jQuery functionality (like
.live() - anything in the 1.7, 1.8, 1.9 and 1.10 category, and if you can in the 3.0 as well to make a future update less likely to break your script) may need to be updated. There were no DOM or other structural changes, so selectors should still be the same.
If you're curious why we're going to jQuery 1.12.4 and not 3.1, this is a matter of incrementally upgrading and making sure things work along the way. Pretty much every 1.x version had major changes, and jQuery recommends upgrading an old 1.x version to the latest 1.12.4 and jquery-migrate 1.x plugin first and fix anything that is deprecated. We are in this stage now and want to make sure everything still works.