Textual form controls—like <input>s, <select>s, and <textarea>s—are styled with the .form-control class. Included are styles for general appearance, focus state, sizing, and more.
For file inputs, swap the .form-control for .form-control-file.
Sizing
Readonly
Readonly plain text
If you want to have <input readonly> elements in your form styled as plain text, use the .form-control-plaintext class to remove the default form field styling and preserve the correct margin and padding.