diff --git a/addons/addon-web-links/src/WebLinkProvider.ts b/addons/addon-web-links/src/WebLinkProvider.ts
index 713f9c2389..66691f44c8 100644
--- a/addons/addon-web-links/src/WebLinkProvider.ts
+++ b/addons/addon-web-links/src/WebLinkProvider.ts
@@ -41,16 +41,18 @@ export class WebLinkProvider implements ILinkProvider {
   }
 }
 
-function baseUrlString(url: URL): string {
-  if (url.password && url.username) {
-    return `${url.protocol}//${url.username}:${url.password}@${url.host}`;
+function isUrl(urlString: string): boolean {
+  try {
+    const url = new URL(urlString);
+    const parsedBase = url.password && url.username
+      ? `${url.protocol}//${url.username}:${url.password}@${url.host}`
+      : url.username
+        ? `${url.protocol}//${url.username}@${url.host}`
+        : `${url.protocol}//${url.host}`;
+    return urlString.toLocaleLowerCase().startsWith(parsedBase.toLocaleLowerCase());
+  } catch (e) {
+    return false;
   }
-
-  if (url.username) {
-    return `${url.protocol}//${url.username}@${url.host}`;
-  }
-
-  return `${url.protocol}//${url.host}`;
 }
 
 export class LinkComputer {
@@ -67,15 +69,7 @@ export class LinkComputer {
       const text = match[0];
 
       // check via URL if the matched text would form a proper url
-      // NOTE: This outsources the ugly url parsing to the browser.
-      // we check if the provided string resembles the URL-parsed one
-      // up to the end of the domain name (ignoring path and params)
-      try {
-        const url = new URL(text);
-        if (!text.startsWith(baseUrlString(url))) {
-          continue;
-        }
-      } catch (e) {
+      if (!isUrl(text)) {
         continue;
       }
 
diff --git a/addons/addon-web-links/src/WebLinksAddon.ts b/addons/addon-web-links/src/WebLinksAddon.ts
index 8902d8e0ad..b3f0548cc1 100644
--- a/addons/addon-web-links/src/WebLinksAddon.ts
+++ b/addons/addon-web-links/src/WebLinksAddon.ts
@@ -18,7 +18,7 @@ import { ILinkProviderOptions, WebLinkProvider } from './WebLinkProvider';
 // - final interpunction like ,.!?
 // - any sort of brackets <>()[]{} (not spec conform, but often used to enclose urls)
 // - unsafe chars from rfc1738: {}|\^~[]`
-const strictUrlRegex = /https?:[/]{2}[^\s"'!*(){}|\\\^<>`]*[^\s"':,.!?{}|\\\^~\[\]`()<>]/;
+const strictUrlRegex = /(https?|HTTPS?):[/]{2}[^\s"'!*(){}|\\\^<>`]*[^\s"':,.!?{}|\\\^~\[\]`()<>]/;
 
 
 function handleLink(event: MouseEvent, uri: string): void {
diff --git a/addons/addon-web-links/test/WebLinksAddon.api.ts b/addons/addon-web-links/test/WebLinksAddon.api.ts
index 5b05ce2e71..99c11600db 100644
--- a/addons/addon-web-links/test/WebLinksAddon.api.ts
+++ b/addons/addon-web-links/test/WebLinksAddon.api.ts
@@ -123,6 +123,21 @@ describe('WebLinksAddon', () => {
       await evalLinkStateData('http://test:password@example.com/some_path?param=1%202%3', { start: { x: 12, y: 1 }, end: { x: 27, y: 2 } });
     });
   });
+
+  // issue #4964
+  it('uppercase in protocol and host, default ports', async () => {
+    const data = `  HTTP://EXAMPLE.COM  \\r\\n` +
+      `  HTTPS://Example.com  \\r\\n` +
+      `  HTTP://Example.com:80  \\r\\n` +
+      `  HTTP://Example.com:80/staysUpper  \\r\\n` +
+      `  HTTP://Ab:xY@abc.com:80/staysUpper  \\r\\n`;
+    await writeSync(page, data);
+    await pollForLinkAtCell(3, 0, `HTTP://EXAMPLE.COM`);
+    await pollForLinkAtCell(3, 1, `HTTPS://Example.com`);
+    await pollForLinkAtCell(3, 2, `HTTP://Example.com:80`);
+    await pollForLinkAtCell(3, 3, `HTTP://Example.com:80/staysUpper`);
+    await pollForLinkAtCell(3, 4, `HTTP://Ab:xY@abc.com:80/staysUpper`);
+  });
 });
 
 async function testHostName(hostname: string): Promise<void> {