The tool itself works fine.
However, Firefox doesn't show me a captcha anymore.
I deactivated all extensions one after the other and found this extension as the source of the error.
Previously, cookies were deleted and cache emptied.

I am not getting the Firefox problems others are reporting (I am UK) and find this extension incredibly useful. Even if it does collect data on what you're interested in it will not be any more than all the other sites you go to anyway so if it saves me money (and it has) it's well worth it.
I really like that for 3rd parties it includes postage in the calculation (unlike other similar sites or plugins). My only reason for dropping a star is not being able to take UK Amazon wishlists automatically like it can US ones and it's a long process (unless I'm missing something) to go through and remove the tracking once you've bought the item.

Avoid this kind of extensions that can collect what you are looking on the internet, it's just collecting informations on you to profile you and similar customers to target ads/products/services. That's desguished spyware in counterpart to provide you a pretended nice service.

And just about the service provided: this kind of extensions (lots of similar exist like this one) can modify the webpages on-the-fly and also can censure some parts or search results to guide you to buy to a specific seller instead of a concurrent. And guess who is paying the extension editor to do that?

Mind again before addin browser extensions!

Added it to a new Firefox installation today. Does not show up on any Amazon Smile page I visit. Very disappointing as it worked fine on Chrome.

Sadly as noted by many others, just doesn't work for AU. Clicking the tiny add-on icon just opens up a blank pop-up window with 2 tabs that do absolutely nothing

Goood

It doesn't work.

Even when trying products that are best selling. It was recommended to me by a friend and its a shame It doesn't work in firefox

On Firefox 85.0.2 (64-bit) using my MacMini 2018, I get the message "Service Temporarily Unavailable" on any Amazon UK listing... I have tried several listings and get the same message. This add-on is nothing more than useless. However, the website is an amazing tool in itself - it's a shame the add on is not what is described.

No support for Amazon Australia, pop up page blank on FF browswer