Prevhost.exe is a file associated with Preview Handlers, and is safe to run on your PC. Microsoft Windows is a range of graphical operating system families developed by Microsoft. First released 32 years ago, it once had an over 90 percent market share in the personal computer segment, and today is available in 133 different languages. Windows and Office Preview Handler Pack is one such custom previewers or preview handlers that provides support for.cs,.aspx and.sql source codes. With the handler pack installed, you can just click on the file ending with extension of.cs,.aspx and.sql with preview pane on, and instantly view the file content in the preview pane.
-->This topic explains how to register a preview handler associated with a given data type. For the purposes of illustration, examples in this topic use a .xyz file type. Registration of a preview handler is a standard file association-based registration.
Instructions
Step 1:
First, a file name extension is associated with a ProgID. The following entry associates the xyzfile ProgID subkey with the .xyz file name extension.
The xyzfile ProgID subkey is stored with the other ProgIDs as shown here:
Each preview handler ProgID subkey contains a subkey named shellex that contains a subkey always named {8895b1c6-b41f-4c1c-a562-0d564250836f}. The presence of that subkey tells the system that the handler is a preview handler.
The default value of the {8895b1c6-b41f-4c1c-a562-0d564250836f} subkey is the class identifier (CLSID) of your handler. An example of the xyzfile ProgID subkey is shown here, associating a handler of CLSID {ec3a629a-a47c-4245-bc78-b4b63d0e3154}.
Step 2:
Next, add the subkey under CLSID for your preview handler. An example is shown here. An explanation of individual entries follows.
The default value for your subkey (here, {ec3a629a-a47c-4245-bc78-b4b63d0e3154}) is not required or used. However, setting it to a nonlocalized string can help you to debug registration issues.
The minus sign (-101) in the .dll resource in the DisplayName entry exists for legacy reasons. The Icon entry, on the other hand, does not require a minus sign.
The AppID value gives a reference to the AppID of the application associated with the file name extension (stored under HKEY_CLASSES_ROOTAPPID. The value used here—{6d2b5079-2f0b-48dd-ab7f-97cec514d30b}—is the ID of the Prevhost.exe surrogate host. 32-bit preview handlers should use AppID {534A1E02-D58F-44f0-B58B-36CBED287C7C} when installed on 64-bit operating systems.
The entries under the InprocServer32 subkey include a reference back to the file name extension's ProgID subkey as well as an entry for a VersionIndependentProgID.
Step 3:
Preview Handlers Windows 10
Finally, the preview handler must be added to the list of all preview handlers. This list is used as an optimization by the system to enumerate all registered preview handlers for display purposes. Again, the default value is not required, it simply aids in the debugging process.
Note
In Windows 7, if the application is installed for all users of the computer, use HKEY_LOCAL_MACHINE; if for only one user, use HKEY_CURRENT_USER.
Related topics
The PDF Shell component in Acrobat and Acrobat Reader allows you to see the thumbnails of PDF documents in Windows explorer, on both 64-bit and 32-bit versions of Windows. By default, this feature is OFF. You can enable it using a specific setting available in the preferences.
Note:
For Acrobat XI and Reader XI, the thumbnails of PDFs are automatically shown in Windows Explorer on Windows 32-bit systems. However, the same is not supported on Windows 64-bit systems.
Preview Handler Fix Tool
Open Acrobat or Acrobat Reader. On the Edit menu, choose Preferences.
In the Preferences dialog box, choose General in the Categories list, and then select the Enable PDF thumbnail previews in Windows Explorer check box.
Note:
If you don't see the Enable PDF thumbnail previews in Windows Explorer checkbox, update your Acrobat DC or Acrobat Reader DC to the latest version. To automatically update from the product, choose Help > Check for updates and then follow the steps in the Updater window to download and install the latest updates.
Wait for a few seconds while Acrobat is configured to show thumbnail previews in Windows Explorer.
Note:
In Acrobat Reader, you see a prompt asking for the feature to be added to the current installation. Click Yes to confirm.