How to check File System Access API support

A website may ask you to open, save, or edit a file, but the file picker does not appear or a feature is missing. The browser may not support the File System Access API, or the page may not be allowed to use it.

You can check the browser's reported features, then test the specific API methods and file workflow you need. The Browser Info tool provides a quick starting point, but testing the actual site matters because browser settings and page security can affect access.

Check File System Access API support

1. Open the Browser Info tool and review its supported-features information. Look for File System Access or file picker entries if they are listed. This gives you a general view of the browser, but the list may not name every API method.
2. For a more specific check, open the browser's developer tools on a secure page. Right-click the page, choose the inspection option, and open the Console. Enter typeof window.showOpenFilePicker. The result function means the browser exposes the file-open picker method. The result undefined means it does not expose that method in this page.
3. Check the other methods you need in the same way. Enter typeof window.showSaveFilePicker to check the save picker, or typeof window.showDirectoryPicker to check directory selection. Support for one method does not guarantee support for the others.
4. Check whether the page is secure by entering window.isSecureContext in the Console. A result of true means it is a secure context. These APIs generally require a secure context, such as an HTTPS page, and may also be unavailable inside a restricted frame.
5. Try the file-open or file-save action on the site where you need it. If a picker opens, choose a harmless test file or cancel the picker. A method showing as available does not prove that the site's code, permissions, or complete workflow will work.

The Console check only reads whether a method exists. It does not open a picker, grant permission, or read a file.

What the result means

The method returns function

Your current browser page exposes that method. The site can still fail to use it if the page is not secure, the call is blocked by a frame or browser policy, or the site does not request access in response to a user action.

The method returns undefined

The browser does not expose that method in the current context. Check that you are testing the browser and profile you actually use, then try a current version of another browser. Browser Info can help confirm which browser and version you are testing.

One method works, but another does not

This is partial support. A site that can open a file may not be able to save directly to a chosen location or select a directory. Ask the site's support team which methods it requires, or use its standard file upload or download option if available.

The method exists, but the picker does not open

The API is present, but the workflow may be blocked. Many picker calls need to follow a direct action such as a click. A site's permission, an embedded frame, or a browser policy can also prevent the request. Check the site itself rather than relying only on the method check.

How to fix a failed check

1. Confirm the browser and profile. Test in the browser where the problem occurs, not only in a different browser or a private window. Extensions, managed profiles, and privacy settings can change what a page can do.
2. Use the secure version of the site. Open the HTTPS address, not an HTTP version. If the site is running inside another page, ask whether it can be opened directly, since an embedded frame may have restricted access.
3. Review the site's permissions. Open the site controls beside the address bar, then review its site settings for file access or file editing permissions if your browser provides them. Labels and available controls vary by browser and version. If you changed a permission, reload the page and try again.
4. Update and restart the browser. Install an available browser update, close and reopen it, and repeat the method check. A browser feature list describes the browser you tested, so an old version can give a different result from a current one.
5. Try a direct user action. If the site has an open or save control, click it yourself rather than expecting a picker to open automatically when the page loads. These APIs are designed to give the user control over file selection.
6. Check whether the device is managed. A work or school browser may have policies that restrict file access. If permissions are locked or the same site works on a personal browser but not a managed one, ask the administrator before changing security controls.

There is not usually a general Windows 11 or macOS switch that adds a missing browser API. On phones and tablets, test the exact browser and site you plan to use, since desktop support does not guarantee that the same file workflow is available on mobile.

Why a support check is not a file access test

The File System Access API lets a website request that you select a file or directory, or choose where to save a file. The browser keeps the choice under your control and may ask for permission before allowing later access. A feature check can tell you whether a method is exposed, but it cannot show whether a particular page will request permission correctly or whether its file handling will succeed.

If the API check passes but saving behaves differently between browsers, see Why file saving works in one browser but not another. The difference may come from the site's fallback behavior or from browser-specific permission rules.