Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.

ajax_example_form_node_form_alter in modules/examples/ajax_example/ajax_example_node_form_alter.inc
Implements hook_form_FORM_ID_alter().
bartik_form_system_theme_settings_alter in core/modules/color/color.legacy.inc
Alters the theme settings form for Bartik legacy colors.
block_form_form_test_alter_form_alter in core/modules/simpletest/tests/form_test.module
Implements hook_form_FORM_ID_alter() on behalf of block.module.
book_form_node_delete_confirm_alter in core/modules/book/book.module
Implements hook_form_FORM_ID_alter().
book_form_node_form_alter in core/modules/book/book.module
Implements hook_form_BASE_FORM_ID_alter().
ckeditor5_form_filter_admin_format_form_alter in core/modules/ckeditor5/ckeditor5.module
Implements hook_form_FORM_ID_alter().
ckeditor5_form_filter_format_editor_image_form_alter in core/modules/ckeditor5/ckeditor5.module
Implements hook_form_FORM_ID_alter().
ckeditor5_form_filter_format_editor_link_form_alter in core/modules/ckeditor5/ckeditor5.module
Implements hook_form_FORM_ID_alter().
ckeditor_form_filter_format_editor_image_form_alter in core/modules/ckeditor/ckeditor.module
Implements hook_form_FORM_ID_alter().
color_form_system_theme_settings_alter in core/modules/color/color.module
Implements hook_form_FORM_ID_alter().
comment_form_node_form_alter in core/modules/comment/comment.module
Implements hook_form_BASE_FORM_ID_alter().
comment_form_node_type_form_alter in core/modules/comment/comment.module
Implements hook_form_FORM_ID_alter().
contact_form_user_admin_settings_alter in core/modules/contact/contact.module
Implements hook_form_FORM_ID_alter().
contact_form_user_profile_form_alter in core/modules/contact/contact.module
Implements hook_form_FORM_ID_alter().
date_form_field_ui_field_edit_form_alter in core/modules/date/date.module
Implements hook_form_FORM_ID_alter() for field_ui_field_edit_form().
date_form_views_exposed_form_alter in core/modules/date/date.module
Implements hook_form_FORM_ID_alter() for views_exposed_form().
date_form_views_ui_edit_form_alter in core/modules/date/date.module
Implements hook_form_FORM_ID_alter() for views_ui_edit_form().
dblog_form_system_logging_settings_alter in core/modules/dblog/dblog.module
Implements hook_form_FORM_ID_alter() for system_logging_settings().
field_ui_form_node_type_form_alter in core/modules/field_ui/field_ui.module
Implements hook_form_FORM_ID_alter().
filter_formtest_form_filter_format_editor_link_form_alter in core/modules/filter/tests/filter_formtest.module
Implements hook_form_FORM_ID_alter().
form_test_form_form_test_alter_form_alter in core/modules/simpletest/tests/form_test.module
Implements hook_form_FORM_ID_alter().
form_test_form_form_test_state_persist_alter in core/modules/simpletest/tests/form_test.module
Implements hook_form_FORM_ID_alter().
form_test_form_user_register_form_alter in core/modules/simpletest/tests/form_test.module
Implements hook_form_FORM_ID_alter() for the registration form.
image_form_system_file_system_settings_alter in core/modules/image/image.module
Implements hook_form_FORM_ID_alter().
list_form_field_ui_field_edit_form_alter in core/modules/field/modules/list/list.module
Implements hook_form_FORM_ID_alter().
locale_form_language_admin_add_form_alter in core/modules/locale/locale.module
Implements hook_form_FORM_ID_alter() for language_admin_add_form(().
locale_form_language_admin_edit_form_alter in core/modules/locale/locale.module
Implements hook_form_FORM_ID_alter() for language_admin_edit_form().
locale_form_language_admin_overview_form_alter in core/modules/locale/locale.module
Implements hook_form_FORM_ID_alter() for language_admin_overview_form().
locale_form_node_form_alter in core/modules/locale/locale.module
Implements hook_form_BASE_FORM_ID_alter().
locale_form_redirect_edit_form_alter in core/modules/redirect/redirect.module
Implements hook_form_FORM_ID_alter() on behalf of locale.module.
menu_form_node_form_alter in core/modules/menu/menu.module
Implements hook_form_BASE_FORM_ID_alter().
menu_form_node_type_form_alter in core/modules/menu/menu.module
Implements hook_form_FORM_ID_alter().
minimal_form_install_configure_form_alter in core/profiles/minimal/minimal.profile
Implements hook_form_FORM_ID_alter() for install_configure_form().
node_access_test_form_node_form_alter in core/modules/node/tests/node_access_test/node_access_test.module
Implements hook_form_BASE_FORM_ID_alter().
node_form_search_form_alter in core/modules/node/node.module
Implements hook_form_FORM_ID_alter().
node_form_system_themes_admin_form_alter in core/modules/node/node.module
Implements hook_form_FORM_ID_alter().
path_form_node_form_alter in core/modules/path/path.module
Implements hook_form_BASE_FORM_ID_alter() for node_form().
path_form_node_type_form_alter in core/modules/path/path.module
Implements hook_form_FORM_ID_alter().
path_form_taxonomy_form_term_alter in core/modules/path/path.module
Implements hook_form_FORM_ID_alter() for taxonomy_form_term().
path_form_taxonomy_form_vocabulary_alter in core/modules/path/path.module
Implements hook_form_FORM_ID_alter() for taxonomy_form_vocabulary().
path_form_user_admin_settings_alter in core/modules/path/path.module
Implements hook_form_FORM_ID_alter() for user_admin_settings().
search_form_layout_block_configure_form_alter in core/modules/search/search.module
Implements hook_form_FORM_ID_alter().
session_test_form_user_login_alter in core/modules/simpletest/tests/session_test.module
Implements hook_form_FORM_ID_alter().
standard_form_install_configure_form_alter in core/profiles/standard/standard.profile
Implements hook_form_FORM_ID_alter() for install_configure_form().
syslog_form_system_logging_settings_alter in core/modules/syslog/syslog.module
Implements hook_form_FORM_ID_alter().
system_form_form_test_alter_form_alter in core/modules/simpletest/tests/form_test.module
Implements hook_form_FORM_ID_alter() on behalf of system.module.
system_form_user_profile_form_alter in core/modules/system/system.module
Implements hook_form_FORM_ID_alter().
system_form_user_register_form_alter in core/modules/system/system.module
Implements hook_form_FORM_ID_alter().
translation_form_node_form_alter in core/modules/translation/translation.module
Implements hook_form_BASE_FORM_ID_alter() for node_form().
translation_form_node_type_form_alter in core/modules/translation/translation.module
Implements hook_form_FORM_ID_alter() for node_type_form().
update_form_system_modules_alter in core/modules/update/update.module
Implements hook_form_FORM_ID_alter() for system_modules().
user_form_field_ui_field_edit_form_alter in core/modules/user/user.module
Implements hook_form_FORM_ID_alter().
user_form_test_form_user_profile_form_alter in core/modules/user/tests/user_form_test/user_form_test.module
Implements hook_form_FORM_ID_alter().
views_form_views_exposed_form_alter in core/modules/views/views.module
Implement hook_form_alter for the exposed form.