Alternative metrics for a paper, include not just the citations in other academic journals, but also all Twitter mentions, citations in Wikipedia, citations across the Stack Exchange network, etc.
The company Altmetric is one of the companies that shows the altmetrics for papers, and it has been mentioned in the answer to this Academia.SE question: Finding all communication related to any research paper.
It used to be as simple as installing the Altmetric extension for your web browser, which creates a bookmarklet (a tiny icon at the top of the web browser) on which you can click to get all the altmetrics. I used this for many years and find out extremely useful. However what if I'm using a browser at, for example a library computer where a network administrator has blocked me from installing custom extensions? Is there a place where I can just copy and paste the URL for the paper's DOI and get the altmetric data, just like Google Scholar allows you to see which papers have cited your paper without installing any browser extension?
It seems that while Altmetric still offers this bookmarklet for free it's still just a bookmarklet that has to be installed, rather than just a place where you can copy and paste a URL of the paper. Furthermore they now seem to want the user's email address, which I'm sure many people will not be delighted to do, as they would certainly find themselves automatically subscribed to get emails which they may not desire.
How can altmetrics for a paper be found without installing anything and without giving away your email address?