diff --git a/extensions/html-language-features/client/src/customData.ts b/extensions/html-language-features/client/src/customData.ts
new file mode 100644
index 00000000000..5e7c1c99c16
--- /dev/null
+++ b/extensions/html-language-features/client/src/customData.ts
@@ -0,0 +1,56 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as path from 'path';
+import { workspace, WorkspaceFolder } from 'vscode';
+
+interface ExperimentalConfig {
+	experimental?: {
+		custom?: {
+			tags?: string[];
+			attributes?: string[];
+		}
+	};
+}
+
+export function getCustomDataPathsInAllWorkspaces(workspaceFolders: WorkspaceFolder[] | undefined) {
+	const tagPaths: string[] = [];
+	const attributePaths: string[] = [];
+
+	if (!workspaceFolders) {
+		return {
+			tagPaths,
+			attributePaths
+		};
+	}
+
+	workspaceFolders.forEach(wf => {
+		const allHtmlConfig = workspace.getConfiguration(undefined, wf.uri);
+		const wfHtmlConfig = allHtmlConfig.inspect<ExperimentalConfig>('html');
+
+		if (
+			wfHtmlConfig &&
+			wfHtmlConfig.workspaceFolderValue &&
+			wfHtmlConfig.workspaceFolderValue.experimental &&
+			wfHtmlConfig.workspaceFolderValue.experimental.custom
+		) {
+			if (wfHtmlConfig.workspaceFolderValue.experimental.custom.tags) {
+				wfHtmlConfig.workspaceFolderValue.experimental.custom.tags.forEach(t => {
+					tagPaths.push(path.resolve(wf.uri.fsPath, t));
+				});
+			}
+			if (wfHtmlConfig.workspaceFolderValue.experimental.custom.attributes) {
+				wfHtmlConfig.workspaceFolderValue.experimental.custom.attributes.forEach(a => {
+					attributePaths.push(path.resolve(wf.uri.fsPath, a));
+				});
+			}
+		}
+	});
+
+	return {
+		tagPaths,
+		attributePaths
+	};
+}
diff --git a/extensions/html-language-features/client/src/htmlMain.ts b/extensions/html-language-features/client/src/htmlMain.ts
index 0b84091bed7..0b4a33b776b 100644
--- a/extensions/html-language-features/client/src/htmlMain.ts
+++ b/extensions/html-language-features/client/src/htmlMain.ts
@@ -13,6 +13,7 @@ import { LanguageClient, LanguageClientOptions, ServerOptions, TransportKind, Re
 import { EMPTY_ELEMENTS } from './htmlEmptyTagsShared';
 import { activateTagClosing } from './tagClosing';
 import TelemetryReporter from 'vscode-extension-telemetry';
+import { getCustomDataPathsInAllWorkspaces } from './customData';
 
 namespace TagCloseRequest {
 	export const type: RequestType<TextDocumentPositionParams, string, any, any> = new RequestType('html/tag');
@@ -49,23 +50,7 @@ export function activate(context: ExtensionContext) {
 	let documentSelector = ['html', 'handlebars', 'razor'];
 	let embeddedLanguages = { css: true, javascript: true };
 
-	let tagPaths: string[] = workspace.getConfiguration('html').get('experimental.custom.tags', []);
-	let attributePaths: string[] = workspace.getConfiguration('html').get('experimental.custom.attributes', []);
-
-	if (tagPaths && tagPaths.length > 0) {
-		if (!workspace.workspaceFolders) {
-			tagPaths = [];
-		} else {
-			try {
-				const workspaceRoot = workspace.workspaceFolders[0].uri.fsPath;
-				tagPaths = tagPaths.map(d => {
-					return path.resolve(workspaceRoot, d);
-				});
-			} catch (err) {
-				tagPaths = [];
-			}
-		}
-	}
+	let { tagPaths, attributePaths } = getCustomDataPathsInAllWorkspaces(workspace.workspaceFolders);
 
 	// Options to control the language client
 	let clientOptions: LanguageClientOptions = {
diff --git a/extensions/html-language-features/package.json b/extensions/html-language-features/package.json
index 01299004ebb..ca3320124e5 100644
--- a/extensions/html-language-features/package.json
+++ b/extensions/html-language-features/package.json
@@ -33,11 +33,11 @@
       "properties": {
         "html.experimental.custom.tags": {
           "type": "array",
-          "description": "A list of JSON file paths that define custom tags."
+          "description": "A list of JSON file paths that define custom tags. Only workspace folder setting will be read."
         },
         "html.experimental.custom.attributes": {
           "type": "array",
-          "description": "A list of JSON file paths that define custom attributes."
+          "description": "A list of JSON file paths that define custom attributes. Only workspace folder setting will be read."
         },
         "html.format.enable": {
           "type": "boolean",