What Is XCF? GIMP's Project Format in Plain English

What XCF is in plain English

XCF is the native format of GIMP, the free image editor often called "the open-source Photoshop." When you draw, retouch a photo or build a collage in GIMP and hit "Save," the program stores all of your work as a .xcf file.

The key phrase is "all of your work." An ordinary PNG or JPG holds a single flat picture: what you see. XCF holds the kitchen behind that picture — every layer, mask and path kept separately, so tomorrow you can come back and redo any detail without losing a thing.

Why "XCF" and what Berkeley has to do with it

The name sounds cryptic, but there is a real story behind it. XCF stands for eXperimental Computing Facility — the name of a computer lab at the University of California, Berkeley. That is where, in the mid-1990s, two students, Spencer Kimball and Peter Mattis, began writing GIMP as a school project. The lab where it all started gave its name to the format — a kind of signature from the authors baked into every file.

The first full version of GIMP shipped in 1998, and XCF has grown alongside the editor ever since: layer groups were added, color precision improved, denser compression arrived. But the essence never changed — it is a snapshot of your desk inside the editor.

"Project" vs "picture": the key difference

The easiest way to understand XCF is to compare it with a finished format like PNG. Picture a cake. PNG is a photo of the finished cake: beautiful, but you can no longer change the filling. XCF is the recipe with every ingredient on its own shelf: the sponge, the cream and the berries are separate, and you can swap a berry or change the cream whenever you like.

In digital graphics those "ingredients" are layers. The logo on one layer, the background on another, the shadow on a third. As long as everything is laid out in layers, the image is easy to edit. Save it as PNG and the layers "bake" together into a single image, like a cake in the oven. There is no getting them back. That is why you keep the XCF until the very end of the job.

What is stored inside an XCF file

XCF tries to remember literally everything you did in GIMP. It is not just pixels — it is the full set of project objects:

• Layers — with their position, opacity and blend modes (such as "multiply" or "screen").
• Layer masks — black-and-white stencils that hide or reveal parts of a layer without erasing them for good.
• Channels — including the alpha transparency channel and any saved selections.
• Paths — vector curves used to outline objects; they stay editable.
• Guides and the grid — lines for precise alignment.
• Color profile, selection and "parasites" — the metadata GIMP attaches to the image.

That is exactly why an XCF reopened in GIMP looks precisely as you left it: with the active selection, the right guides and every layer in place. It is a "save game" in the fullest sense.

Compression and size: why the files are heavy

XCF is a lossless format: it does not throw away detail to save space the way JPG does. Internally the picture is split into neat 64×64-pixel tiles, and each is compressed with the simple RLE algorithm. Since GIMP 2.10 (2018) the denser zlib compression was added — the same one used in ordinary ZIP archives.

Even with compression, though, an XCF is almost always heavier than the final PNG, and the reason is simple: it stores not one picture but a dozen layers, masks and a history of selections. That is the fair price of flexibility. If a file gets really large, GIMP can save it as .xcf.gz — the same XCF, additionally packed with gzip.

Why you shouldn't send XCF to others

Here lies the format's main trap. XCF is built to fit GIMP's internals perfectly — it literally mirrors how the editor keeps data in memory. For that reason GIMP's own developers explicitly recommend against using XCF as an interchange format.

In practice that means: if you send a .xcf to a client, a colleague or a friend, there is a good chance nothing will open for them. Photoshop doesn't understand it, a browser won't show it, a phone has no preview. XCF is your private working file, not a format for sending around.

How to open and share an XCF

Only GIMP itself opens XCF perfectly — and it is free for Windows, macOS and Linux. XnView MP, ImageMagick and Krita read the format partially, but don't count on them: masks, effects and paths may render incorrectly.

If your goal is not to edit but simply to see the result or pass it along, the most reliable route is to convert the XCF to PNG. Then all visible layers flatten into one picture, transparency is preserved, and the file opens anywhere.

Want the opposite — to turn a plain picture into an editable GIMP project? There is a reverse conversion for that, PNG to XCF. And every supported conversion lives on the all formats page. If you prefer the hands-on side, check out the guide on how to open XCF without GIMP.