What is form field detection?
Definition
Form field detection is the process of automatically locating where a document's input fields belong: text lines, checkboxes, radio options, and signature areas, and classifying each so interactive fields can be placed on the page.
What it produces
Detection returns the position and type of every field it finds, usually as a structured description of the form. That description can then drive placing real interactive fields, or simply tell a downstream system where each value lives.
Why it is hard
Forms vary wildly. Underlines, boxes, grids, and tiny checkboxes all signal inputs differently, and a label can sit above, beside, or inside its field. Reliable detection has to read both the layout and the text to tell a real field from page decoration.
Where it fits
Detection is the first step in turning a flat PDF into a fillable one: find the fields, then place them. The same field description also serves as the contract a program uses to fill the form afterward.