33 files declare their use of FormatterBase

AuthorNameFormatter.php in core/modules/comment/src/Plugin/Field/FieldFormatter/AuthorNameFormatter.php
BaseFieldFileFormatterBase.php in core/modules/file/src/Plugin/Field/FieldFormatter/BaseFieldFileFormatterBase.php
BasicStringFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/BasicStringFormatter.php
BooleanFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/BooleanFormatter.php
CommentDefaultFormatter.php in core/modules/comment/src/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php
ContentModerationStateFormatter.php in core/modules/content_moderation/src/Plugin/Field/FieldFormatter/ContentModerationStateFormatter.php
DateTimeFormatterBase.php in core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
DummyAjaxFormatter.php in core/modules/image/tests/modules/image_module_test/src/Plugin/Field/FieldFormatter/DummyAjaxFormatter.php
DummyImageFormatter.php in core/modules/image/tests/modules/image_module_test/src/Plugin/Field/FieldFormatter/DummyImageFormatter.php
EntityReferenceFormatterBase.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/EntityReferenceFormatterBase.php
FileSize.php in core/modules/file/src/Plugin/Field/FieldFormatter/FileSize.php
LinkFormatter.php in core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php
MailToFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/MailToFormatter.php
NumericFormatterBase.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/NumericFormatterBase.php
NumericUnformattedFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/NumericUnformattedFormatter.php
OEmbedFormatter.php in core/modules/media/src/Plugin/Field/FieldFormatter/OEmbedFormatter.php
OptionsDefaultFormatter.php in core/modules/options/src/Plugin/Field/FieldFormatter/OptionsDefaultFormatter.php
OptionsKeyFormatter.php in core/modules/options/src/Plugin/Field/FieldFormatter/OptionsKeyFormatter.php
StringFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/StringFormatter.php
TelephoneLinkFormatter.php in core/modules/telephone/src/Plugin/Field/FieldFormatter/TelephoneLinkFormatter.php
TestFieldApplicableFormatter.php in core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldApplicableFormatter.php
TestFieldDefaultFormatter.php in core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldDefaultFormatter.php
TestFieldEmptyFormatter.php in core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldEmptyFormatter.php
TestFieldEmptySettingFormatter.php in core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldEmptySettingFormatter.php
TestFieldMultipleFormatter.php in core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldMultipleFormatter.php
TestFieldNoSettingsFormatter.php in core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldNoSettingsFormatter.php
TestFieldPrepareViewFormatter.php in core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldPrepareViewFormatter.php
TextDefaultFormatter.php in core/modules/text/src/Plugin/Field/FieldFormatter/TextDefaultFormatter.php
TextTrimmedFormatter.php in core/modules/text/src/Plugin/Field/FieldFormatter/TextTrimmedFormatter.php
TimestampAgoFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/TimestampAgoFormatter.php
TimestampFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/TimestampFormatter.php
UriLinkFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/UriLinkFormatter.php
UserNameFormatter.php in core/modules/user/src/Plugin/Field/FieldFormatter/UserNameFormatter.php

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