How to Fix ERR_UNKNOWN_URL_SCHEME Error (9 Methods)

ERR_UNKNOWN_URL_SCHEME is a browser error that occurs when a URL’s protocol prefix – the part before :// – is not recognised by the browser or the system handling the request. Standard prefixes like http:// and https:// are always supported. The error triggers when links use schemes such as tel:, mailto:, skype:, zoom:, or custom application-specific protocols that either lack a registered handler or are blocked by a browser configuration issue.

The error has been documented as a persistent Chromium bug since Chrome 40 and affects all Chromium-based browsers, including Chrome, Edge, and Opera. It appears both in desktop browsers and inside Android WebView – the component that lets native apps display web content without launching a separate browser.

According to Malwarebytes’ July 2025 browser extension security report, 2.3 million Chrome and Edge users were affected by malicious extensions that intercepted and modified browser behaviour – the same class of interference that can trigger URL scheme errors in otherwise healthy browsers.

What Causes the ERR_UNKNOWN_URL_SCHEME Error?

Several conditions can produce this error, and identifying the right one determines which fix to apply first:

How to Fix ERR_UNKNOWN_URL_SCHEME in Chrome: 9 Methods

Work through these fixes in order. Most users resolve the error within the first three methods.

Method 1: Clear Browser Cache and Cookies

Corrupted cache data is the most common non-extension cause of URL scheme errors. Clearing it forces Chrome to re-process the request from scratch.

1. Click the three-dot menu (⋮) in Chrome’s top-right corner
2. Go to Settings > Privacy and security
3. Click Clear browsing data
4. Set the time range to All time
5. Check Cookies and other site data and Cached images and files
6. Click Clear data, then restart Chrome and retry the link

Method 2: Disable Chrome Extensions

Extensions that intercept web requests – ad blockers, redirect managers, VPN extensions – frequently cause this error by mishandling non-HTTP scheme links. Turning them off isolates whether an extension is the cause.

1. Type chrome://extensions/ in the address bar
2. Toggle every extension off
3. Retry the problematic link
4. If the error is gone, re-enable extensions one at a time until you find the culprit

For context on why this matters: security researchers identified at least 16 malicious Chrome extensions affecting over 3.2 million users that actively modified how browsers handled URLs, according to GitLab’s February 2025 browser extension threat analysis. Even well-intentioned extensions can produce the same interference without malicious intent.

Method 3: Create a New Chrome User Profile

A corrupted user profile stores broken settings that persist even after clearing cache. A new profile starts completely clean.

1. Click your profile picture in the top-right corner of Chrome
2. Select Add to create a new profile
3. Complete the brief setup
4. Test the same link in the new profile

If the link works in the new profile, your original profile data is the source of the problem.

Method 4: Disable Hardware Acceleration

Hardware acceleration routes certain browser tasks to the GPU. In some system configurations, this creates a conflict with how URL requests are processed.

1. Open Chrome Settings
2. Click Advanced > System
3. Turn off Use hardware acceleration when available
4. Restart Chrome completely, then test the link

Method 5: Check URL Formatting

A malformed URL is often the simplest explanation. Chrome cannot process a URL whose scheme is misspelled or structurally broken.

Common formatting mistakes to check:

Copy the URL into a text editor and inspect the first five to ten characters carefully before trying anything else.

Method 6: Install the Required Application

Links using tel:, mailto:, zoom:, or whatsapp: schemes require a corresponding installed application to function. If the app is missing, the browser cannot hand off the request.

Install the relevant app, set it as the default handler for that scheme, and retry the link.

Method 7: Try a Different Browser

Testing in Firefox, Microsoft Edge, or Safari confirms whether the issue is Chrome-specific or tied to the link or website itself. If the link works in another browser, return to Chrome and continue with Methods 8 or 9.

Method 8: Reset Chrome to Default Settings

Resetting Chrome removes all custom configurations – including any that might be blocking URL scheme resolution – without touching your bookmarks or saved passwords.

1. Open Chrome Settings
2. Click Advanced > Reset and clean up
3. Select Restore settings to their original defaults
4. Click Reset settings

Restart Chrome after the reset completes before testing the link again.

Method 9: Fix WebView Implementation (Developers Only)

Android’s WebView component natively handles only http:// and https://. Any other scheme – tel:, mailto:, whatsapp:, custom app protocols – requires explicit handling in the app’s code. Without it, WebView throws net::ERR_UNKNOWN_URL_SCHEME and the request fails.

Option A – Override URL loading with shouldOverrideUrlLoading:

@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
    if (url.startsWith("http://") || url.startsWith("https://")) {
        view.loadUrl(url);
        return true;
    }
    // Handle custom schemes via Android Intent
    Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
    startActivity(intent);
    return true;
}

Option B – Open external links in a new window using target=”_blank”:

<a href="https://example.com" target="_blank">Visit Example</a>

This keeps WebView focused on HTTP/HTTPS content while passing non-standard schemes to the system’s registered app handlers. Note that opening new windows can disrupt the in-app user experience; use Android intents wherever possible for a cleaner implementation.

Option C – Disable non-standard URL schemes entirely:

If your app does not need to handle tel:, mailto:, or custom protocols, filter them out explicitly in shouldOverrideUrlLoading and show a toast message to the user instead of failing silently.

How Do You Prevent ERR_UNKNOWN_URL_SCHEME From Happening Again?

Once the error is fixed, a few habits prevent it from recurring:

When Should You Contact Support?

Most ERR_UNKNOWN_URL_SCHEME errors are resolved on the user side. Contact the website or app’s support team if the error persists after completing all nine methods, if other users are reporting the same link as broken, or if the website’s links consistently use malformed or unsupported scheme formats. A persistent error across multiple browsers and devices is almost always a server-side or link configuration issue, not a local browser problem.

FAQs about ERR_UNKNOWN_URL_SCHEME Error

What exactly causes the ERR_UNKNOWN_URL_SCHEME error?

The error appears when a URL’s protocol prefix – such as tel:, mailto:, whatsapp:, or a custom app scheme – is not recognized by Chrome or the operating system. Chrome stops the request rather than attempt to process an unknown instruction. The error has been documented as a Chromium bug since Chrome version 40 and can also be triggered by corrupted cache, conflicting extensions, or misconfigured Android WebView in native apps.

How do I fix ERR_UNKNOWN_URL_SCHEME in Chrome quickly?

Start by clearing your browser cache – go to Settings > Privacy and security > Clear browsing data, select all time, check cached images and cookies, and click Clear data. If that doesn’t resolve it, disable all Chrome extensions at chrome://extensions/ and re-enable them one by one. These two steps resolve the error for the majority of users without needing to go further.

Is ERR_UNKNOWN_URL_SCHEME a virus or security risk?

The error itself is not a virus and does not indicate a security breach. It is a browser protection mechanism that stops Chrome from executing unrecognised URL protocols. However, if the error appears alongside unexpected redirects or browser behaviour changes, check your extensions for malicious code – security researchers documented over 3.2 million Chrome users affected by extensions that silently modified URL handling as recently as early 2025.

Why does ERR_UNKNOWN_URL_SCHEME appear in Android apps?

Android’s WebView component only natively supports http:// and https:// schemes. When an app tries to open a link using tel:, mailto:, whatsapp:, or a custom protocol without explicitly handling it in code, WebView cannot process the request and returns net::ERR_UNKNOWN_URL_SCHEME. The fix requires the developer to implement shouldOverrideUrlLoading and route non-standard schemes to Android’s Intent system.

Can malware cause the ERR_UNKNOWN_URL_SCHEME error?

Yes. Malicious Chrome extensions that intercept and rewrite URL requests can trigger this error. If you suspect malware, run a full antivirus scan, remove any recently installed or suspicious extensions, and create a new Chrome user profile to test whether the error clears. Resetting Chrome to default settings also removes malicious configuration changes that might be causing URL scheme failures.

How do I stop ERR_UNKNOWN_URL_SCHEME from reappearing?

Keep Chrome updated, audit your extensions regularly, clear cache monthly, and avoid clicking links that use non-HTTP protocols unless the corresponding app is installed. For developers, implementing proper URL scheme handling in shouldOverrideUrlLoading is the only reliable way to prevent WebView from throwing this error in production apps.

Priya Mervana

Verified Web Security Experts

Priya Mervana is working at SSLInsights.com as a web security expert with over 10 years of experience writing about encryption, SSL certificates, and online privacy. She aims to make complex security topics easily understandable for everyday internet users.