diff --git a/src/Controller/Controller_Custom_Fonts.php b/src/Controller/Controller_Custom_Fonts.php
index 7943b3dcd..0aa997f0f 100644
--- a/src/Controller/Controller_Custom_Fonts.php
+++ b/src/Controller/Controller_Custom_Fonts.php
@@ -85,7 +85,7 @@ class Controller_Custom_Fonts extends Helper_Abstract_Controller {
 	 * @var string[] List of the standard font keys used when saving settings
 	 * @since 6.0
 	 */
-	protected $font_keys = [ 'regular', 'italics', 'bold', 'bolditalics' ];
+	protected $font_keys = Model_Custom_Fonts::FONT_STYLES;
 
 	public function __construct( Model_Custom_Fonts $model, LoggerInterface $log, Helper_Abstract_Form $gform, string $font_dir_path, string $filesystem = 'GFPDF_Vendor\\GravityPdf\\Upload\\Storage\\FileSystem', string $file = 'GFPDF_Vendor\\GravityPdf\\Upload\\File' ) {
 		$this->model         = $model;
@@ -428,7 +428,7 @@ public function update_item( WP_REST_Request $request ) {
 			}
 
 			/* Not one an upload was just saved under, which happens when the old file had gone missing */
-			array_map( [ $this, 'delete_font_file' ], array_diff( $unused_files, $uncommitted_files ) );
+			$this->delete_unused_font_files( array_diff( $unused_files, $uncommitted_files ) );
 
 			$uncommitted_files = [];
 
@@ -554,15 +554,16 @@ public function delete_item( WP_REST_Request $request ) {
 			}
 
 			/* Delete TTF files from disk */
-			$font = $this->model->get_font_by_id( $id );
+			$font  = $this->model->get_font_by_id( $id );
+			$files = [];
 			foreach ( $this->font_keys as $font_id ) {
-				if ( empty( $font[ $font_id ] ) ) {
-					continue;
+				if ( ! empty( $font[ $font_id ] ) ) {
+					$files[] = basename( $font[ $font_id ] );
 				}
-
-				$this->delete_font_file( basename( $font[ $font_id ] ) );
 			}
 
+			$this->delete_unused_font_files( $files );
+
 			/* Update DB */
 			if ( ! $this->model->delete_font( $id ) ) {
 				throw new GravityPdfDatabaseUpdateException();
@@ -739,6 +740,30 @@ protected function get_upload_error_message( File $file, string $error_code = Er
 		return __( 'The upload is not a valid TTF file', 'gravity-pdf' );
 	}
 
+	/**
+	 * Delete font files, keeping any another site's fonts use (the fonts folder is network-wide)
+	 *
+	 * @param string[] $files The filenames
+	 *
+	 * @since 6.19.0
+	 */
+	protected function delete_unused_font_files( array $files ): void {
+		if ( $files === [] ) {
+			return;
+		}
+
+		$shared = $this->model->get_files_used_by_other_sites();
+
+		foreach ( $files as $file ) {
+			if ( in_array( $file, $shared, true ) ) {
+				$this->log->debug( 'Kept a font file another site uses', [ 'file' => $file ] );
+				continue;
+			}
+
+			$this->delete_font_file( $file );
+		}
+	}
+
 	/**
 	 * @param string $file The filename of the font to be deleted
 	 *
diff --git a/src/Model/Model_Custom_Fonts.php b/src/Model/Model_Custom_Fonts.php
index debe2b553..713004a7f 100644
--- a/src/Model/Model_Custom_Fonts.php
+++ b/src/Model/Model_Custom_Fonts.php
@@ -28,12 +28,24 @@
  */
 class Model_Custom_Fonts extends Helper_Abstract_Model {
 
+	/**
+	 * @var string[] The keys a font record stores its files under
+	 * @since 6.19.0
+	 */
+	public const FONT_STYLES = [ 'regular', 'italics', 'bold', 'bolditalics' ];
+
 	/**
 	 * @var Helper_Abstract_Options
 	 * @since 6.0
 	 */
 	protected $options;
 
+	/**
+	 * @var array<int, string[]> The files other sites' fonts use, keyed by the current site ID
+	 * @since 6.19.0
+	 */
+	protected $files_used_by_other_sites = [];
+
 	public function __construct( Helper_Abstract_Options $options ) {
 		$this->options = $options;
 	}
@@ -158,6 +170,70 @@ public function delete_font( string $id ): bool {
 		return $this->options->update_option( 'custom_fonts', $fonts );
 	}
 
+	/**
+	 * The filenames the other sites' fonts use, read from each site's options table to avoid switch_to_blog()
+	 *
+	 * @return string[]
+	 *
+	 * @since 6.19.0
+	 */
+	public function get_files_used_by_other_sites(): array {
+		global $wpdb;
+
+		if ( ! is_multisite() ) {
+			return [];
+		}
+
+		$current_site = get_current_blog_id();
+		if ( isset( $this->files_used_by_other_sites[ $current_site ] ) ) {
+			return $this->files_used_by_other_sites[ $current_site ];
+		}
+
+		$site_ids = get_sites(
+			[
+				'fields'       => 'ids',
+				'number'       => 0,
+				'site__not_in' => [ $current_site ],
+			]
+		);
+
+		$files = [];
+
+		foreach ( $site_ids as $site_id ) {
+			$prefix   = $wpdb->get_blog_prefix( $site_id );
+			$settings = maybe_unserialize( $wpdb->get_var( "SELECT option_value FROM {$prefix}options WHERE option_name = 'gfpdf_settings' LIMIT 1" ) ); //phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared
+
+			if ( ! is_array( $settings ) || ! is_array( $settings['custom_fonts'] ?? null ) ) {
+				continue;
+			}
+
+			foreach ( $settings['custom_fonts'] as $font ) {
+				if ( ! is_array( $font ) ) {
+					continue;
+				}
+
+				foreach ( self::FONT_STYLES as $style ) {
+					if ( is_string( $font[ $style ] ?? null ) && $font[ $style ] !== '' ) {
+						$files[] = basename( $font[ $style ] );
+					}
+				}
+			}
+		}
+
+		$this->files_used_by_other_sites[ $current_site ] = array_values( array_unique( $files ) );
+
+		return $this->files_used_by_other_sites[ $current_site ];
+	}
+
+	/**
+	 * Forget the other sites' font files read this request
+	 *
+	 * @since 6.19.0
+	 */
+	public function flush(): void {
+		$this->files_used_by_other_sites = [];
+	}
+
 	/**
 	 * Checks if the ID already exists and, if so, suffixes the ID with a string until unique
 	 *
diff --git a/src/Model/Model_Font_Sources.php b/src/Model/Model_Font_Sources.php
index d8d4c01f6..624852743 100644
--- a/src/Model/Model_Font_Sources.php
+++ b/src/Model/Model_Font_Sources.php
@@ -4,7 +4,6 @@
 
 namespace GFPDF\Model;
 
-use GFPDF\Helper\Fonts\FlushCache;
 use GFPDF\Helper\Helper_Abstract_Model;
 use GFPDF\Helper\Helper_Data;
 use GFPDF\Statics\Git_Blob;
@@ -668,7 +667,7 @@ protected function get_record_file_names(): array {
 
 		$names = [];
 		foreach ( $records as $record ) {
-			foreach ( [ 'regular', 'italics', 'bold', 'bolditalics' ] as $style ) {
+			foreach ( Model_Custom_Fonts::FONT_STYLES as $style ) {
 				$file = is_string( $record[ $style ] ?? null ) ? basename( $record[ $style ] ) : '';
 				if ( isset( $family_files[ $file ] ) ) {
 					$names[ $file ] = $file;
@@ -1032,39 +1031,30 @@ public function adopt_records( string $source_id ): array {
 	}
 
 	/**
-	 * Remove a custom font record, and outside Multisite its files too: another site's record may use the shared fonts
-	 * folder. Logs and returns false on failure
+	 * Remove a custom font record and the files no other site uses. Logs and returns false on failure
 	 *
 	 * @since 6.19.0
 	 */
 	protected function remove_record( string $id ): bool {
-		$removed = false;
-		$error   = '';
+		$error = '';
 
 		try {
-			if ( ! is_multisite() ) {
-				$removed = GPDFAPI::delete_pdf_font( $id ) === true;
-			} elseif ( $this->custom_fonts->delete_font( $id ) ) {
-				FlushCache::flush( $id );
-				$removed = true;
+			if ( GPDFAPI::delete_pdf_font( $id ) === true ) {
+				return true;
 			}
 		} catch ( Throwable $e ) {
 			$error = $e->getMessage();
 		}
 
-		if ( ! $removed ) {
-			$this->log->error(
-				'Could not remove a custom font record replaced by a font source',
-				[
-					'font'      => $id,
-					'exception' => $error,
-				]
-			);
-
-			return false;
-		}
+		$this->log->error(
+			'Could not remove a custom font record replaced by a font source',
+			[
+				'font'      => $id,
+				'exception' => $error,
+			]
+		);
 
-		return true;
+		return false;
 	}
 
 	/**
diff --git a/tests/phpunit/Concerns/CopiesFontFixtures.php b/tests/phpunit/Concerns/CopiesFontFixtures.php
index 0a587afad..602e3bbdc 100644
--- a/tests/phpunit/Concerns/CopiesFontFixtures.php
+++ b/tests/phpunit/Concerns/CopiesFontFixtures.php
@@ -5,7 +5,6 @@
 namespace GFPDF\Tests\Concerns;
 
 use GFPDF\Helper\Fonts\FlushCache;
-use GFPDF\Model\Model_Custom_Fonts;
 use GFPDF\Model\Model_Font_Sources;
 use GFPDF\Statics\Git_Blob;
 use GPDFAPI;
@@ -98,8 +97,8 @@ protected function add_record( string $id, array $files ): void {
 	/**
 	 * A model whose bundled source accepts the fixture as a legacy Arimo copy
 	 */
-	protected function get_model_with_legacy( string $fixture, ?Model_Custom_Fonts $custom_fonts = null ): Model_Font_Sources {
-		$model = new class( GPDFAPI::get_data_class(), $custom_fonts ?? GPDFAPI::get_mvc_class( 'Model_Custom_Fonts' ), GPDFAPI::get_log_class() ) extends Model_Font_Sources {
+	protected function get_model_with_legacy( string $fixture ): Model_Font_Sources {
+		$model = new class( GPDFAPI::get_data_class(), GPDFAPI::get_mvc_class( 'Model_Custom_Fonts' ), GPDFAPI::get_log_class() ) extends Model_Font_Sources {
 			/** @var array<string, int> */
 			public $legacy = [];
 
@@ -294,6 +293,7 @@ protected function remove_font_fixtures(): void {
 		array_map( [ FlushCache::class, 'flush' ], array_unique( $this->recorded_fonts ) );
 		GPDFAPI::get_mvc_class( 'Model_Font_Sources' )->flush();
 		GPDFAPI::get_mvc_class( 'Model_Required_Fonts' )->flush();
+		GPDFAPI::get_mvc_class( 'Model_Custom_Fonts' )->flush();
 
 		/* A download or its fallback caches metrics under every font key the render asked for, substitutes included */
 		if ( $this->requested !== [] ) {
diff --git a/tests/phpunit/integration/Controller/Test_Controller_Custom_Fonts.php b/tests/phpunit/integration/Controller/Test_Controller_Custom_Fonts.php
index 1c80a1ca0..64e1d2002 100644
--- a/tests/phpunit/integration/Controller/Test_Controller_Custom_Fonts.php
+++ b/tests/phpunit/integration/Controller/Test_Controller_Custom_Fonts.php
@@ -883,6 +883,101 @@ public function test_delete_item_with_font_reference_gone_success() {
 		$this->assertSame( 200, $response->get_status() );
 	}
 
+	/**
+	 * @group ms-required
+	 */
+	public function test_deleting_a_font_keeps_the_files_another_site_uses() {
+		global $gfpdf;
+
+		$this->skipWithoutMultisite();
+
+		[ $shared, $own, $other_site ] = $this->share_a_file_with_another_site();
+
+		$this->assertNull( $this->controller->delete_item( $this->delete_request( 'font' ) ) );
+
+		$this->assertSame( [], $this->model->get_custom_fonts() );
+		$this->assertFileExists( $shared );
+		$this->assertFileDoesNotExist( $own );
+		$this->assertArrayHasKey( 'other', get_blog_option( $other_site, 'gfpdf_settings' )['custom_fonts'] );
+
+		/* The last site using the file removes it */
+		switch_to_blog( $other_site );
+		$gfpdf->options->set_plugin_settings();
+		$response = $this->controller->delete_item( $this->delete_request( 'other' ) );
+		restore_current_blog();
+		$gfpdf->options->set_plugin_settings();
+
+		$this->assertNull( $response );
+		$this->assertFileDoesNotExist( $shared );
+	}
+
+	/**
+	 * @group ms-required
+	 */
+	public function test_update_item_keeps_a_replaced_file_another_site_uses() {
+		$this->skipWithoutMultisite();
+
+		[ $shared, $own, $other_site ] = $this->share_a_file_with_another_site();
+
+		$request = new WP_REST_Request( 'POST' );
+		$request->set_body_params(
+			[
+				'id'   => 'font',
+				'bold' => '',
+			]
+		);
+		$this->set_font_files( $request, [ 'regular' => [ 'DejaVuSans.ttf', self::$test_fonts[0] ] ] );
+
+		$updated = $this->controller->update_item( $request );
+
+		$this->assertNotSame( $shared, $updated['regular'] );
+		$this->assertSame( '', $updated['bold'] );
+		$this->assertFileExists( $shared );
+		$this->assertFileDoesNotExist( $own );
+	}
+
+	/**
+	 * Save a font whose regular file another site's font also uses, and whose bold file is only its own
+	 *
+	 * @return array{0: string, 1: string, 2: int} The shared file, the font's own file and the other site's ID
+	 */
+	protected function share_a_file_with_another_site(): array {
+		$shared = $this->copy_font( 0, 'Shared.ttf' );
+		$own    = $this->copy_font( 1, 'Own.ttf' );
+		$this->model->add_font( $this->font_record( 'font', $shared, $own ) );
+
+		$other_site = self::factory()->blog->create();
+		update_blog_option( $other_site, 'gfpdf_settings', [ 'custom_fonts' => [ 'other' => $this->font_record( 'other', $shared ) ] ] );
+
+		return [ $shared, $own, $other_site ];
+	}
+
+	protected function copy_font( int $fixture, string $name ): string {
+		copy( self::$test_fonts[ $fixture ], $this->tmp_font_location . $name );
+
+		return $this->tmp_font_location . $name;
+	}
+
+	protected function font_record( string $id, string $regular, string $bold = '' ): array {
+		return [
+			'id'          => $id,
+			'font_name'   => $id,
+			'regular'     => $regular,
+			'italics'     => '',
+			'bold'        => $bold,
+			'bolditalics' => '',
+			'useOTL'      => 0x00,
+			'useKashida'  => 0,
+		];
+	}
+
+	protected function delete_request( string $id ): WP_REST_Request {
+		$request = new WP_REST_Request( 'DELETE' );
+		$request->set_param( 'id', $id );
+
+		return $request;
+	}
+
 	public function test_delete_item_invalid_font_id() {
 		wp_set_current_user( $this->admin_user );
 
diff --git a/tests/phpunit/integration/Model/Test_Model_Custom_Fonts.php b/tests/phpunit/integration/Model/Test_Model_Custom_Fonts.php
index 8c6aa2e52..3504d7231 100644
--- a/tests/phpunit/integration/Model/Test_Model_Custom_Fonts.php
+++ b/tests/phpunit/integration/Model/Test_Model_Custom_Fonts.php
@@ -198,4 +198,64 @@ public function data_has_unique_font_id(): array {
 			[ true, 'dejavusans1' ],
 		];
 	}
+
+	/**
+	 * @group ms-excluded
+	 */
+	public function test_a_single_site_reads_no_other_sites_fonts() {
+		global $wpdb;
+
+		$this->skipWithMultisite();
+
+		$queries = $wpdb->num_queries;
+
+		$this->assertSame( [], $this->model->get_files_used_by_other_sites() );
+		$this->assertSame( $queries, $wpdb->num_queries );
+	}
+
+	/**
+	 * @group ms-required
+	 */
+	public function test_get_files_used_by_other_sites() {
+		global $wpdb;
+
+		$this->skipWithoutMultisite();
+
+		$this->model->add_font(
+			[
+				'id'      => 'mine',
+				'regular' => '/fonts/Mine.ttf',
+			]
+		);
+
+		$fonts = [
+			'one'     => [
+				'regular'     => '/fonts/One.ttf',
+				'bolditalics' => '/fonts/Shared.ttf',
+			],
+			'two'     => [
+				'regular' => '',
+				'italics' => '/fonts/Shared.ttf',
+				'bold'    => [ 'Array.ttf' ],
+			],
+			'corrupt' => 'font',
+		];
+
+		update_blog_option( self::factory()->blog->create(), 'gfpdf_settings', [ 'custom_fonts' => $fonts ] );
+		update_blog_option( self::factory()->blog->create(), 'gfpdf_settings', [ 'custom_fonts' => 'fonts' ] );
+		update_blog_option( self::factory()->blog->create(), 'gfpdf_settings', 'settings' );
+		self::factory()->blog->create();
+
+		/* A truncated serialized value */
+		$truncated = self::factory()->blog->create();
+		update_blog_option( $truncated, 'gfpdf_settings', [ 'custom_fonts' => [] ] );
+		$wpdb->update( $wpdb->get_blog_prefix( $truncated ) . 'options', [ 'option_value' => 'a:1:{s:12:"custom_fonts";a:1:{' ], [ 'option_name' => 'gfpdf_settings' ] );
+
+		$this->assertSame( [ 'One.ttf', 'Shared.ttf' ], $this->model->get_files_used_by_other_sites() );
+
+		/* Read once a request */
+		$queries = $wpdb->num_queries;
+		$this->model->get_files_used_by_other_sites();
+		$this->assertSame( $queries, $wpdb->num_queries );
+	}
 }
diff --git a/tests/phpunit/integration/Model/Test_Model_Font_Sources.php b/tests/phpunit/integration/Model/Test_Model_Font_Sources.php
index 8cac6882a..dd20ff3a2 100644
--- a/tests/phpunit/integration/Model/Test_Model_Font_Sources.php
+++ b/tests/phpunit/integration/Model/Test_Model_Font_Sources.php
@@ -4,7 +4,6 @@
 
 namespace GFPDF\Model;
 
-use GFPDF\Exceptions\GravityPdfIdException;
 use GFPDF\Tests\Concerns\CopiesFontFixtures;
 use GFPDF\Tests\Concerns\Seamed_Font_Downloader;
 use GFPDF\Tests\Concerns\UnregistersMvcClasses;
@@ -427,10 +426,8 @@ public function test_adopt_records_removes_a_record_matching_the_manifest() {
 
 		$this->assertSame( [ 'dejavusanscondensed' ], $this->model->adopt_records( 'core' ) );
 		$this->assertSame( [], $this->custom_fonts->get_custom_fonts() );
-
-		/* Multisite keeps the files in the shared fonts folder */
-		$this->assertSame( is_multisite(), is_file( $this->font_dir . 'DejaVuSansCondensed85274.ttf' ) );
-		$this->assertSame( is_multisite(), is_file( $this->font_dir . 'DejaVuSans-Bold.ttf' ) );
+		$this->assertFileDoesNotExist( $this->font_dir . 'DejaVuSansCondensed85274.ttf' );
+		$this->assertFileDoesNotExist( $this->font_dir . 'DejaVuSans-Bold.ttf' );
 	}
 
 	public function test_adopt_records_removes_a_record_of_the_core_font_installers_files() {
@@ -486,7 +483,7 @@ public function test_adopt_records_removes_a_record_matching_legacy_hashes() {
 
 		$this->assertSame( [ 'arimo' ], $model->adopt_records( 'bundled' ) );
 		$this->assertSame( [], $this->custom_fonts->get_custom_fonts() );
-		$this->assertSame( is_multisite(), is_file( $this->font_dir . 'Arimo-Regular85274.ttf' ) );
+		$this->assertFileDoesNotExist( $this->font_dir . 'Arimo-Regular85274.ttf' );
 	}
 
 	public function test_adopt_records_keeps_an_edited_record() {
@@ -933,10 +930,6 @@ public function test_adopt_records_logs_a_record_it_could_not_remove() {
 	}
 
 	public function test_adopt_records_keeps_the_record_when_the_custom_fonts_controller_is_unhooked() {
-		if ( is_multisite() ) {
-			$this->markTestSkipped( 'Multisite removes the record through the model' );
-		}
-
 		$model = $this->get_model_with_legacy( 'Chewy.ttf' );
 		$this->copy_fixture( 'Chewy.ttf', 'Arimo-Regular.ttf' );
 		$this->add_record( 'arimo', [ 'regular' => 'Arimo-Regular.ttf' ] );
@@ -952,22 +945,22 @@ function () use ( $model ) {
 		$this->assertFileExists( $this->font_dir . 'Arimo-Regular.ttf' );
 	}
 
-	public function test_adopt_records_logs_a_record_removed_elsewhere_on_multisite() {
-		if ( ! is_multisite() ) {
-			$this->markTestSkipped( 'Single site removes the record through the API' );
-		}
-
-		$custom_fonts = new class( GPDFAPI::get_options_class() ) extends Model_Custom_Fonts {
-			public function delete_font( string $id ): bool {
-				throw new GravityPdfIdException();
-			}
-		};
+	/**
+	 * @group ms-required
+	 */
+	public function test_adopt_records_keeps_a_file_another_site_uses() {
+		$this->skipWithoutMultisite();
 
-		$model = $this->get_model_with_legacy( 'Chewy.ttf', $custom_fonts );
+		$model = $this->get_model_with_legacy( 'Chewy.ttf' );
 		$this->copy_fixture( 'Chewy.ttf', 'Arimo-Regular.ttf' );
 		$this->add_record( 'arimo', [ 'regular' => 'Arimo-Regular.ttf' ] );
 
-		$this->assert_record_kept( $model->adopt_records( 'bundled' ) );
+		$other_site = self::factory()->blog->create();
+		update_blog_option( $other_site, 'gfpdf_settings', [ 'custom_fonts' => $this->custom_fonts->get_custom_fonts() ] );
+
+		$this->assertSame( [ 'arimo' ], $model->adopt_records( 'bundled' ) );
+		$this->assertSame( [], $this->custom_fonts->get_custom_fonts() );
+		$this->assertFileExists( $this->font_dir . 'Arimo-Regular.ttf' );
 	}
 
 	public function test_adopt_records_moves_on_after_an_error_removing_a_record() {