What Web Preferences API does and why you might want it
Web Preferences API is a Chrome feature that lets websites detect your personal settings — things like whether you prefer dark mode, reduced motion, or high contrast. When you turn it on, websites can read these preferences from your operating system and adjust automatically without you having to change settings on each site separately.
The API itself does not collect data about you or send information anywhere. It only lets a website see preferences you have already set in Windows, macOS, or Linux. You stay in control: you can turn the feature on or off at any time, and you can block individual websites from reading your preferences even if the API is enabled globally.
Most people do not need to enable this manually. Chrome turns it on by default in recent versions. But if you have disabled it or use an older version, these steps will show you how to turn it back on.
Key Takeaways
- Web Preferences API is on by default in Chrome version 96 and later, so you may not need to do anything.
- You can check whether it is enabled by typing chrome://flags in the address bar and searching for "Web Preferences API".
- If it shows "Default", the feature is on; if it shows "Disabled", you can change it to "Default" or "Enabled".
- Turning on the API does not share your data — it only lets websites read preferences you have already set in your operating system.
- You can block individual websites from using the API even when it is globally enabled by using Chrome's site settings.
Check if Web Preferences API is already on
Open Chrome and type chrome://flags in the address bar, then press Enter. This opens Chrome's experimental features page.
In the search box at the top, type "Web Preferences API" and wait for the results to load. You will see one entry labeled "Web Preferences API". Look at the dropdown menu next to it. If it says "Default", the feature is already on. If it says "Disabled", follow the next section to turn it on.
Enable Web Preferences API if it is turned off
Find the "Web Preferences API" entry on the flags page. Click the dropdown menu next to it and select either "Default" or "Enabled". Both will turn the feature on; "Default" means Chrome decides based on your version, while "Enabled" forces it on.
Chrome will ask you to relaunch the browser. Click the blue "Relaunch" button at the bottom right of the screen. Chrome will close and reopen automatically, and the change will take effect.
What websites can see when the API is on
When Web Preferences API is enabled, websites can detect four things from your operating system: whether you prefer dark mode, whether you want reduced motion (useful if animations make you uncomfortable), whether you prefer high contrast, and whether you have set your system to use a light or dark color scheme.
Websites cannot see your passwords, browsing history, location, or any other personal information. They only see the four accessibility and appearance preferences you have already chosen in your system settings. A website cannot turn these preferences on or off — it can only read what you have set.
Block specific websites from reading your preferences
Even with the API enabled, you can prevent individual websites from using it. Go to the website you want to block, click the lock icon in the address bar, then click "Site settings".
Scroll down to find "Sensors" or look for a setting related to "Preferences API". Click the dropdown and select "Block". That website will no longer be able to read your system preferences, even though the API is globally enabled.
Turn off Web Preferences API entirely
If you want to disable the feature completely, go back to chrome://flags, search for "Web Preferences API", and click the dropdown next to it. Select "Disabled".
Chrome will ask you to relaunch. Click the blue "Relaunch" button, and the browser will restart with the API turned off. No website will be able to read your system preferences until you turn it back on.
Why you might want this feature on
The main reason to enable Web Preferences API is convenience. If you use dark mode on your computer, websites that support the API will automatically switch to dark mode when you visit them — you do not have to find and click a dark mode button on every site. The same applies to high contrast or reduced motion settings.
For people with motion sensitivity or visual processing differences, having websites respect your reduced motion preference can make browsing more comfortable. Websites that support the API will skip animations and transitions automatically.
Frequently Asked Questions
Does enabling Web Preferences API share my data with websites?
No. The API only lets websites read preferences you have already set in your operating system. It does not send any information to Chrome, Google, or anywhere else. You remain in control — you can block individual websites from reading your preferences at any time.
What if a website does not support Web Preferences API?
Nothing changes. The website will look the same as it always does. The API only works on websites that have been built to use it. Most major sites are adding support, but not all sites use it yet.
Can I turn Web Preferences API on and off without restarting Chrome?
No. Chrome requires a full restart whenever you change a flag setting. The relaunch button will close and reopen the browser automatically, so you do not have to do it manually.
If I block a website from using the API, can it still see my other settings?
Blocking the API only prevents that website from reading your system preferences through this specific feature. The website can still see other information like your browser type or screen size, which are not part of the Preferences API.
Does Web Preferences API work on mobile Chrome?
Web Preferences API is available on Chrome for Android and iOS, but the flags page works differently on mobile. On Android, you can type chrome://flags in the address bar the same way. On iOS, the feature may not be adjustable through flags — it depends on your iOS version.