diff --git a/CHANGELOG.md b/CHANGELOG.md
index 69c3051c..1b24d650 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 - Upgraded codemirror from version 5 to version 6
 - Add code editor to allow editing the entire style
 - Add support for sprite object in setting modal
+- Allow root-relative urls in the stylefile
 - _...Add new stuff here..._
 
 ### 🐞 Bug fixes
diff --git a/src/libs/urlopen.test.ts b/src/libs/urlopen.test.ts
index 3dc4c5db..6ee7a310 100644
--- a/src/libs/urlopen.test.ts
+++ b/src/libs/urlopen.test.ts
@@ -36,6 +36,12 @@ describe("validate", () => {
     });
   });
 
+  describe("when URL is root relative", () => {
+    it("should return ErrorType.None", () => {
+      expect(validate("/static/style.json")).toBe(ErrorType.None);
+    });
+  });
+
   describe("when window.location.protocol is https:", () => {
     beforeEach(() => {
       Object.defineProperty(window.location, "protocol", {
diff --git a/src/libs/urlopen.ts b/src/libs/urlopen.ts
index 86c27a8b..e7aa5bec 100644
--- a/src/libs/urlopen.ts
+++ b/src/libs/urlopen.ts
@@ -45,8 +45,13 @@ function getProtocolSafe(url: string): { protocol?: string, isLocal?: boolean }
   }
 };
 
-export function validate(url: string): ErrorType {
-  if (url === "") {
+export function validate(url?: string): ErrorType {
+  if (!url) {
+    return ErrorType.None;
+  }
+
+  // allow root-relative URLs ("/static/style.json") but do not allow protocol-relative URLs ("//example.com")
+  if (url.startsWith("/") && !url.startsWith("//")) {
     return ErrorType.None;
   }