The fields

Options every field accepts

Key	Default	Description
type	—	Required. Field type
name	—	Required. Storage key
label	''	Visible label
instructions	''	Help text below the label
required	false	Shows the asterisk and adds required to the control
default_value	''	Value used before anything has been saved
placeholder	''	Placeholder text
wrapper	array()	width as a percentage, plus extra class and id
conditional_logic	array()	Rules deciding whether the field is shown

Available types

Type	Own options	Notes
text	maxlength, prepend, append
textarea	rows, maxlength	Keeps line breaks
number	min, max, step, prepend, append	Empty is stored as '', not 0
range	min, max, step, prepend, append	Slider with a synced number input
email	maxlength, prepend, append	Sanitised with sanitize_email()
url	maxlength, prepend, append	Sanitised with sanitize_url(); print with esc_url()
password	maxlength	Stored in plain text; don't use it for credentials
select	choices, multiple, allow_null	Native, with fixed options
radio	choices, layout, allow_null
checkbox	choices, layout	Stores an array
button_group	choices, layout, allow_null	Radios styled as segmented buttons
true_false	message, ui, ui_on_text, ui_off_text	Stores 1 or 0; ui draws the switch
date_picker	return_format, min, max	Native control; stored as Ymd
time_picker	return_format, min, max	Native control; stored as H:i:s
date_time_picker	return_format, min, max	Native control; stored as Y-m-d H:i:s
color_picker	enable_opacity, palette	Core picker; hex, or rgba() with opacity
wysiwyg	tabs, toolbar, rows, media_upload, table	TinyMCE; works inside repeaters too
link	return_format	Core link modal; stores text, URL and target
oembed	width, height, return_format	Stores the URL; the HTML resolves at render time
image	preview_size, library, mime_types, return_format	Stores the ID; validated against the media library
file	library, mime_types, return_format	Stores the attachment ID
gallery	preview_size, min, max, mime_types, return_format	Ordered list of images
icon_picker	collections, return_format	Iconify search; stores mdi:home
message	message, esc_html, new_lines	Presentation only, stores nothing
separator	—	Presentation only; the label titles the section
tab	selected, endpoint	Groups the fields that follow into a tab
accordion	open, multi_expand, endpoint	Nests the fields that follow into a collapsible panel
repeater	sub_fields, min, max, button_label	List of rows; compatible with ACF's data
group	sub_fields, layout	Sub-fields under a shared name, without repetition
flexible_content	layouts, min, max, button_label	Rows of different shapes, chosen by the editor
clone	clone, display, prefix_name, prefix_label, overrides	Pulls in a field set declared elsewhere
post_object	post_type, taxonomy, post_status, multiple	Stores the post ID; searches over AJAX
page_link	those of post_object	Stores the ID; returns the permalink
relationship	filters, min, max, plus those of post_object	Two panels; preserves order
taxonomy	taxonomy, field_type, hide_empty	Checkboxes, radios or a dropdown
user	role, multiple	Stores the user ID

Every one of them also accepts readonly and disabled.

What each field returns

WordPress hands back every meta value as a string. Forja returns them with their native type:

Type	Returns	When empty
number	int or float	null
range	int or float	the minimum
true_false	bool	false
image, file	per return_format	0, '' or null
checkbox, multiple select	array	array()
repeater, flexible_content	array of rows	array()
group	array keyed by sub-field	array()

An empty number returns null and not 0 on purpose: zero is a legitimate value, and conflating them would make "they didn't touch it" indistinguishable from "they typed zero".

Going deeper

Repeaters, flexible content, clone, conditional logic, the relational fields and the storage formats are documented in Spanish. Start at Los campos.