Log in
The Windows clipboard is a built‑in feature that temporarily stores anything you copy—text, images, files. The clipboard is stored in regular RAM, just like any other application data. There is no dedicated hardware region or special memory bank reserved for it. It is wrapped in OS‑level access control and session isolation.
How Windows Protects Clipboard Data
The Windows clipboard uses normal system memory, not a special protected memory region — but Windows does protect access to it. Only processes running in the same user session can access the
clipboard.
A random background service running as SYSTEM cannot read your clipboard unless it explicitly impersonates your user.
Apps must use the official APIs, see below.
Windows enforces:
Only one process can open the clipboard at a time.
A process must own the clipboard to modify it.
Apps cannot read the clipboard without requesting access.
Technical Details
The Windows clipboard was designed as a mechanism that Microsoft Windows operating systems use to allow data to be shared between applications. It first appeared in Windows 3.1, although its functionality has greatly increased since then.
When you copy something, Windows doesn’t just store the raw bytes. It stores one or more representations of the data, each tagged with a format ID.
A clipboard format tells Windows and applications:
what kind of data is stored
how to interpret it
how to convert it if needed
This is why you can copy text from Word and paste it as plain text, rich text, HTML, or even an image depending on the target app.
Clipboard formats commonly used (CF_TEXT, CF_UNICODETEXT, CF_HDROP, custom formats) are stored as handles to memory blocks.
Microsoft also provides the ability for “private data formats”, custom formats that are application specific (for example, fonts in a word processing program), and that could be registered so that other applications could transfer data in these formats. Two private data formats that are used extensively are object link embedding CF_OLE (0xC013) decimal 49171 and CF_ DataObjects (0xC009) decimal 49161.
For an application to send data to the clipboard, it first allocates a block of global memory using GlobalAlloc, Global- Lock, and GlobalUnlock (Fig. 1). It then opens the clipboard using OpenClipboard, empties it using EmptyClipboard, places the clipboard data using SetClipboard and then closes the clipboard using CloseClipboard (Microsoft.com,). While only one piece of data can be present in the clipboard at any given time, it is possible to send and store that piece of data in multiple formats by performing multiple SetClipboardData functions.
This allows applications that handle data in different ways to all have access to it (e.g., text in Microsoft Word with or without formatting). Once data is in the clipboard, the block of global memory belongs to the clipboard and other pointers to it become invalid. Getting data from the clipboard (Fig. 2) is even easier and involves opening the clipboard, determining which of the available clipboard formats to retrieve (this is an application specific task), retrieving a handle to the data, and then closing the clipboard.
Live look at list all formats when you copy an item.
InsideClipboard - View the content of all formats stored in the Clipboard (nirsoft.net)
Live look at list all formats when you copy an item.
InsideClipboard - View the content of all formats stored in the Clipboard (nirsoft.net)
Open Source: https://doxygen.reactos.org/d0/dd2/win32ss_2user_2ntuser_2clipboard_8c.html#afb1abd5c321fb8e6a65f8994dcec07e1
The clipboard formats defined by the system are called standard clipboard formats. These clipboard formats are described in the following table.
The clipboard formats defined by the system are called standard clipboard formats. These clipboard formats are described in the following table.
| Constant/value | Description |
|---|---|
|
A handle to a bitmap (HBITMAP). |
|
A memory object containing a BITMAPINFO structure followed by the bitmap bits. |
|
A memory object containing a BITMAPV5HEADER structure followed by the bitmap color space information and the bitmap bits. |
|
Software Arts' Data Interchange Format. |
|
Bitmap display format associated with a private format. The hMem parameter must be a handle to data that can be displayed in bitmap format in lieu of the privately formatted data. |
|
Enhanced metafile display format associated with a private format. The hMem parameter must be a handle to data that can be displayed in enhanced metafile format in lieu of the privately formatted data. |
|
Metafile-picture display format associated with a private format. The hMem parameter must be a handle to data that can be displayed in metafile-picture format in lieu of the privately formatted data. |
|
Text display format associated with a private format. The hMem parameter must be a handle to data that can be displayed in text format in lieu of the privately formatted data. |
|
A handle to an enhanced metafile (HENHMETAFILE). |
|
Start of a range of integer values for application-defined GDI object clipboard formats. The end of the range is CF_GDIOBJLAST. Handles associated with clipboard formats in this range are not automatically deleted using the GlobalFree function when the clipboard is emptied. Also, when using values in this range, the hMem parameter is not a handle to a GDI object, but is a handle allocated by the GlobalAlloc function with the GMEM_MOVEABLE flag. |
|
See CF_GDIOBJFIRST. |
|
A handle to type HDROP that identifies a list of files. An application can retrieve information about the files by passing the handle to the DragQueryFile function. |
|
The data is a handle to the locale
identifier associated with text in the clipboard. When you close the
clipboard, if it contains CF_TEXT data but no CF_LOCALE data, the system automatically sets the CF_LOCALE format to the current input language. You can use the CF_LOCALE format to associate a different locale with the clipboard text. An application that pastes text from the clipboard can retrieve this format to determine which character set was used to generate the text. Note that the clipboard does not support plain text in multiple character sets. To achieve this, use a formatted text data type such as RTF instead. The system uses the code page associated with CF_LOCALE to implicitly convert from CF_TEXT to CF_UNICODETEXT. Therefore, the correct code page table is used for the conversion. |
|
Handle to a metafile picture format as defined by the METAFILEPICT structure. When passing a CF_METAFILEPICT handle by means of DDE, the application responsible for deleting hMem should also free the metafile referred to by the CF_METAFILEPICT handle. |
|
Text format containing characters in the OEM character set. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character signals the end of the data. |
|
Owner-display format. The clipboard owner must display and update the clipboard viewer window, and receive the WM_ASKCBFORMATNAME, WM_HSCROLLCLIPBOARD, WM_PAINTCLIPBOARD, WM_SIZECLIPBOARD, and WM_VSCROLLCLIPBOARD messages. The hMem parameter must be NULL. |
|
Handle to a color palette. Whenever an
application places data in the clipboard that depends on or assumes a
color palette, it should place the palette on the clipboard as well. If the clipboard contains data in the CF_PALETTE (logical color palette) format, the application should use the SelectPalette and RealizePalette functions to realize (compare) any other data in the clipboard against that logical palette. When displaying clipboard data, the clipboard always uses as its current palette any object on the clipboard that is in the CF_PALETTE format. |
|
Data for the pen extensions to the Microsoft Windows for Pen Computing. |
|
Start of a range of integer values for private clipboard formats. The range ends with CF_PRIVATELAST. Handles associated with private clipboard formats are not freed automatically; the clipboard owner must free such handles, typically in response to the WM_DESTROYCLIPBOARD message. |
|
See CF_PRIVATEFIRST. |
|
Represents audio data more complex than can be represented in a CF_WAVE standard wave format. |
|
Microsoft Symbolic Link (SYLK) format. |
|
Text format. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character signals the end of the data. Use this format for ANSI text. |
|
Tagged-image file format. |
|
Unicode text format. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character signals the end of the data. |
|
Represents audio data in one of the standard wave formats, such as 11 kHz or 22 kHz PCM. |
