How to fix unwanted JPG to TIFF conversion of clipboard

2 - the clipboard converts it in something it prefers instead of leaving it well alone

What is well alone?

The thing on screen rendered by a browser is not a file. It is image data. A file is just a wrapper for the data. Copying the displayed image data is not the same as copying the file.

If you want a copy of the image file used to render the on-screen image, you need to download that file, not copy the image displayed from the file.

Now the question becomes why non-Apple browsers get penalised with massive file formats and how that can be fixed.

They get what they ask for, or they get what they have chosen, or they get the default because they didn’t ask.

Each of those use entirely different rendering engines. It could be that they render images as compressed bitmaps while WebKit renders as jpg or png.

On Ventura 13.1, when I copy an existing JPG image from my Desktop to the Clipboard, the Finder does not reveal the actual image, but only the filename when asked to Show Clipboard. When I use the Clipboard Viewer available in the Apple Developer additional tools, it shows the following entries:

Only the last four entries show image data (not the image) in the adjacent ASCII/hex viewer. It is clear where the Message application is getting its TIFF image data. Each copy from a web browser will write similar and different content to the clipboard based on that browser developer's choices.

The clipboard will provide various formats for pasting. The receiving application can ask for a particular format. It’s not that the clipboard converts it as it has always provided many formats, it is that Messages asks for tiff.

Sending feedback to Apple (in the order of hundreds of thousands) will be the only way it will change.

Fairpoint. But I didn’t discuss what was stored in the case of copying an image from a webpage, you are not copying the file you were copying the image. If you want the file displayed in a webpage, you should download the file and use that.

You are at the mercy of the browser vendors what formats that they choose to place on the clipboard following a copy operation, especially if they rolled their own Pasteboard routines. You cannot change this behavior as it is compiled into the application. Thus, you would need to contact the individual browser development teams…

As dialabrain and Barney-15E have already noted, any file you're viewing is no longer a file. It's uncompressed data. You can't display any compressed file format as is. It has to be uncompressed to be viewable.

The clipboard is the same. It can't hold a TIFF, JPEG, PSD, PNG or any other image file format because it's not a file in that state. It's uncompressed data waiting to be either put somewhere, or replaced by the next item you copy to the clipboard.

Firefox and Vivaldi and Safari aren't doing anything to the image (TIFF, TIFF, JPG in your example) since, again, it's not a file you're copying to the clipboard. Only uncompressed image data. Pasting that data into any app that can display an image file is still uncompressed data. Until you actually save the pasted data as a file, it isn't any kind of file format.

FWIW, there is nothing to fix. That's how copying an image to the clipboard works, and as you mentioned, has worked for decades.

That's not quite the case. When you copy an image to the clipboard it is stored as an uncompressed bitmap.

I tried. 😎

As I tried to explain in my previous posts, when you copy an image from a web page, it is stored as an uncompressed bitmap (TIFF) in the Clipboard. :)