When comparing Shield UI Upload vs Upload.js, the Slant community recommends Shield UI Upload for most people. In the question“What are the best JavaScript libraries for file uploading?” Shield UI Upload is ranked 1st while Upload.js is ranked 7th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Asynchronous upload
Pro Legacy browser support
Pro Rich templates, API and events
Pro No dependencies
It's very lightweight, and doesn't depend on libraries like jQuery, React, etc.
Pro Integrated cloud storage
Upload.js lets you add uploads to your site in an afternoon - even if you're on a tight deadline from the client, so don't have time to create an AWS account, setup buckets and URL pre-signing etc. You can just creat an Upload.io account, plug-in the API key, and have it all working within the hour.
Pro Progress events
Has progress events that make it easy to add progress bars. They also appear to be smoothed (i.e. 1%, 2%, ... 100%, rather than 7%, 89%, 100%).
Pro Large files
Apparently uses multipart uploads under-the-hood. After checking on the network inspector this seems to be true for larger files at least. Testing it with a ~300MB video it uploads fine.
Cons
Con Not free
Con No free tier
There's a free trial, and there's a "free" API key, but it only stores files temporarily -- ok for hackathons or demos, but if you want to use this in a "real" application, you'll need to pay for an account. (It's $7/mo at the time of writing.)