ERR_UNKNOWN_URL_SCHEME occurs when Chrome encounters a URL protocol it does not recognize or cannot handle. Standard protocols like http://, https://, and file:// work natively in Chrome, but custom schemes like intent://, tel://, mailto://, or app-specific protocols require either a registered handler or an installed application. When no handler exists, Chrome displays this error.
This error appears most often on Android when websites try to open mobile apps using intent:// URLs, but it also affects desktop Chrome when web pages use custom URL schemes for desktop applications (like slack://, zoom://, or steam://). The fix depends on the type of URL scheme causing the error.
What Causes ERR_UNKNOWN_URL_SCHEME
On Android, the most common cause is a website using an intent:// URL to deep-link into a mobile app that is not installed on your device. The intent:// scheme is Android-specific and tells the browser to launch a specific app. If the app is not installed and the website does not provide a fallback URL, Chrome shows ERR_UNKNOWN_URL_SCHEME.
On desktop, this error appears when a website uses a custom protocol handler (like myapp://open) and no application is registered to handle that protocol. Browser extensions or web applications that try to use non-standard URL schemes also trigger this error. Additionally, malformed URLs with typos in the scheme (htps:// instead of https://) produce this error because Chrome does not recognize the misspelled protocol.
Fix 1: Install the Required App (Android)
If the error occurs when tapping a link in Chrome on Android, the website is trying to open a mobile app you do not have installed. Look at the URL in the error, which usually contains the app’s package name (like com.whatsapp or com.instagram.android). Search for that app in the Google Play Store and install it. After installation, tap the link again and Chrome should open the app correctly.
Fix 2: Open the Link in the Default Browser
Some in-app browsers (Facebook, Instagram, Twitter built-in browsers) do not support custom URL schemes that the full Chrome browser handles. If you encounter this error in an in-app browser, tap the menu (three dots) and select “Open in Chrome” or “Open in browser.” The full Chrome browser has better support for protocol handlers and registered apps.
Fix 3: Check for Typos in the URL
Manually typed URLs with scheme typos (htps://, htp://, htttp://) trigger ERR_UNKNOWN_URL_SCHEME. Check the address bar carefully and correct any typos in the protocol portion. The valid web protocols are http:// and https://. If you copied the URL from somewhere, make sure the entire scheme was included in the copy.
Fix 4: Register a Protocol Handler (Desktop)
On desktop, if a specific application’s URL scheme is not recognized, the application may not have registered its protocol handler during installation. Reinstall the application (Zoom, Slack, Steam, Discord, etc.) and make sure to allow it to register as a protocol handler during setup. On Windows, protocol handlers are registered in the Windows Registry under HKEY_CLASSES_ROOT. On macOS, they are defined in the application’s Info.plist file.
Fix 5: Use a Fallback URL
If you are a web developer and users report this error, implement proper fallback handling for custom URL schemes. Instead of directly linking to intent:// or custom protocols, use JavaScript to attempt the custom scheme and fall back to a web URL after a timeout. For Android intent:// links, include the S.browser_fallback_url parameter to specify where Chrome should redirect if the app is not installed.
Frequently Asked Questions
What is a URL scheme?
A URL scheme (also called protocol) is the first part of a URL before the colon, like “https” in https://example.com. It tells the browser or operating system how to handle the resource. Standard web schemes include http, https, ftp, and file. Custom schemes like tel (phone calls), mailto (email), and app-specific schemes (slack, zoom, steam) require registered handlers to function.
Why does ERR_UNKNOWN_URL_SCHEME appear only on some devices?
Different devices have different apps installed and different protocol handlers registered. A link using zoom:// works on a device with Zoom installed but fails on one without it. Similarly, Android devices handle intent:// URLs differently based on installed apps. The error is device-specific, not website-specific.
Can I make Chrome handle custom URL schemes?
Chrome can handle custom schemes if a web application registers as a protocol handler using the navigator.registerProtocolHandler() JavaScript API. Desktop applications register their schemes during installation. You cannot manually add scheme support to Chrome without either a web handler or an installed application that registers the protocol.
