Does it remove the fields?

No. The form still works. Only the values are emptied.

Why were some fields not cleared?

They are read-only or calculated, which is usually deliberate on the form's part.

Is this the same as flattening?

The opposite. Flattening fixes the values in; this takes them out.

forms

Clear a PDF Form

Empty every field, to get a blank form back from a filled one.

Runs in your browser

How it works

Empties the fields and leaves the form intact, which is how you recover a blank template from the only copy you have — a filled one. Read-only and calculated fields cannot be emptied, and the tool says how many it could not clear rather than reporting success it did not achieve.

Related tools

Import PDF Form Values

/import-pdf-form-values

View PDF Form Fields

/view-pdf-form-fields

Flatten Form

/flatten-pdf-form

Questions

Does it remove the fields?: No. The form still works. Only the values are emptied.
Why were some fields not cleared?: They are read-only or calculated, which is usually deliberate on the form's part.
Is this the same as flattening?: The opposite. Flattening fixes the values in; this takes them out.