Windows 11 Is Fixing Blocked PDF Previews in File Explorer - How to Get Them Back Today

File Explorer is getting its PDF previews back - a test build of Windows 11 lets the Preview pane show PDFs you downloaded, a year after a security update switched them off.

It's only in a Windows Insider build for now, so most PCs still block those previews.

Here's why they stopped, the one-minute fix for today, and the captions change in the same builds.

Why Your PDF Previews Stopped

Since the October 14, 2025 security updates, File Explorer refuses to preview files that came from the internet.

Select one and the Preview pane says: "The file you are attempting to preview could harm your computer. If you trust the file and the source you received it from, open it to view its contents."

Microsoft did this to close a hole where a booby-trapped file could leak your Windows sign-in hash - a scrambled copy of your password - just by being previewed. The danger comes from web code hidden inside files, which is why HTML files are the real target.

What the New Build Changes

In the Beta (26H1) build released on November 6, PDFs and other non-HTML files downloaded from the web preview automatically again. HTML files stay blocked.

There's a catch. Windows 11 26H1 is the version made for a new generation of Arm laptops, and Microsoft hasn't said when the change reaches ordinary Windows 11 PCs. You can read the full notes on the Windows Insider blog.

Fix It Today: Unblock the File

1. Open the file's properties. Right-click the PDF in File Explorer and choose Properties.
2. Tick Unblock. On the General tab, at the bottom next to Security, tick Unblock and click OK.
3. Sign out if it's still blocked. Microsoft says the change may only take effect after you next sign in to Windows.

Still a Blank Preview Pane? Add a PDF Previewer

The Preview pane can only show a PDF if an installed app adds a PDF preview handler. If it stays empty even for PDFs you made yourself, that's the missing piece.

• PowerToys. Microsoft's free toolkit adds PDF previews and thumbnails under File Explorer add-ons, and its Peek tool opens a quick preview of any selected file with Ctrl+Space.
• Adobe Acrobat Reader. The free reader adds its own PDF preview to File Explorer when you install it.

Live Captions Now Lets You Pick What It Hears

Live captions types out whatever your PC is playing - a video, a podcast, a call - in a bar on your screen. Until now it listened to system audio, with your microphone as an optional extra.

In the new Beta and Experimental builds, you choose system audio, your microphone or both. That means you can caption a conversation in the room without it also picking up the video playing in the background.

You can use Live captions today on Windows 11 22H2 or later. Press Windows + Ctrl + L, let it download the speech files the first time, and it starts captioning anything that plays.

Everything Else in This Week's Builds

• A shortcut to your user folder. Type ~ in the File Explorer address bar to jump to your user folder, or ~AppData to go one level deeper.
• Magnifier on more than one screen. In Beta (26H1), each monitor keeps its own zoom level, and a new contrast theme cuts glare without changing photos or videos.
• Windows Hello in the dark. Face sign-in can briefly brighten your screen in a dim room, and in Experimental builds you no longer wait for face or fingerprint before typing your PIN.
• Beta moves to 26H2. The Beta channel jumps to build 26320 through a small enablement update, with no big changes on its own.

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