By default, the SignalR buffer is set at about 18KB in a new Razor Components application.
This limits how much data you can transfer between Browser and Server as you will see errors such as this if you overflow this buffer:
|System.InvalidOperationException: Advancing examined to the end would cause pipe to deadlock because FlushAsync is waiting.|
I am not advocating always changing these values, and I'm not saying set them to zero - but I have certainly been able to upload 13MB images this way. YMMV.
Choose a buffer size that works for you seems to be the current advice.
I have created a sample project on Github https://github.com/SQL-MisterMagoo/RCFileUpload
This project simply demonstrates how to upload multiple image files to the server and displays a gallery of images.
After working on this for a while, I found this old post https://www.radzen.com/blog/read-image-base64-blazor-signalr/ by Vladimir Enchev, which takes a similar, approach - but slightly different in that their code only handles single file uploads at a time, while my sample shows a method for handling multiple files. But I would recommend reading Vladimir's post - the more information you get, the better your understanding.