Chrome: I can't recall the last time I didn't install an extension from the Google's Chrome Web Store. However, developers - up until now - have been allowed to offer their extensions as inline downloads. In other words, they could drop a download button on a website, you'd click on it and see a typical installation confirmation dialogue (as if you were installing the extension from the Chrome Web Store itself), and before you knew it, you were +1 to extensions.
Screenshot: David Murphy
Goodbye, inline installations
This inline installation feature, as it's known, is going away because we can't have nice things. With inline installations, developers could talk about an extension any way they wanted to on their websites. Presumably, you then wouldn't pay that much attention to the actual description of the extension you were grabbing from the Chrome Web Store.
That could lead to a little confusion, at best, or maliciousness, at worst, if a developer wanted to pull the ol' swippy-swappy and con you into installing something shady. As Google writes:
... we continue to receive large volumes of complaints from users about unwanted extensions causing their Chrome experience to change unexpectedly - and the majority of these complaints are attributed to confusing or deceptive uses of inline installation on websites. As we've attempted to address this problem over the past few years, we've learned that the information displayed alongside extensions in the Chrome Web Store plays a critical role in ensuring that users can make informed decisions about whether to install an extension. When installed through the Chrome Web Store, extensions are significantly less likely to be uninstalled or cause user complaints, compared to extensions installed through inline installation.
As of today, developers will not be allowed to offer inline installations for newly published extensions. Existing extensions will find inline installations disabled starting September 12, and Google will deprecate the entire inline install API when Chrome 71 hits in early December 2018.
What Google's change means for you
If you visit a chrome extension developer's website and find that you can't click on a download button and install an extension, Google's adjustment is likely to blame.
Before you give up on the extension, try searching the Chrome Web Store manually to see if the extension exists - it should, unless the developer has made it very clear that this is an extension you should sideload into your browser. (You really shouldn't have to do that unless there's no other way to get a particular extension that you must have and have verified that the extension isn't malware in disguise.)
If Google pulls your favourite extension from the Chrome Web Store, for example, and you don't care about the security concerns involved with installing an extension "gone rogue", sideloading the extension allows you to to bypass Google's installation restrictions.
To begin, enter
chrome://extensions/ into your address bar and click on the "developer mode" toggle in the upper-right corner.
Screenshot: David Murphy
Take the extension's .CRX file that you previously downloaded - assuming you have one - and use a service such as CRX Extractor to transform its contents into a simple ZIP.
Unzip that archive somewhere on your desktop or laptop, then click on "Load Unpacked" in the
chrome://extensions/ window and go find the folder where you extracted that ZIP file. Barring any errors, that should drop the extension directly into Chrome.
If you have no idea where to find .CRX files for extensions, you can check out the ever-useful Chrome Extensions Archive. Download a .ZIP file from here, rename it to .CRX, and go through the above process to manually drop it into your browser. Yes, you'll still have to use CRX Extractor to create another ZIP and import that folder's contents into your browser. You'll be fine.
(Though, really, you should just use the Chrome Web Store whenever possible for extensions. Malware can slip in, but at least Google is vigilant about checking for it and removing it.)