How does Firefox reader view operate

Question

Summary

I am looking for the criteria by which I can create a webpage and be [fairly] sure it will appear in the Firefox

Answer 1

You need at least one

tag around the text, that you want to see in Reader View, and at least 516 characters in 7 words inside the text.

for example this will trigger the ReaderView:

 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
 123456789 123456

See my example at https://stackoverflow.com/a/30750212/1069083