How to Merge Layers in GIMP

When you are done building a composition in GIMP, you often need to combine layers before exporting. GIMP gives you three main ways to do this - Merge Down, Merge Visible, and Flatten Image. Each does something slightly different, and using the wrong one at the wrong time can cause problems.

Merge Down - Combining Two Adjacent Layers

Merge Down combines the active layer with the layer directly below it in the stack. The result is a single layer that shows both layers flattened together.

How to use it:

1. Click the top layer of the two you want to merge in the Layers panel.
2. Right-click and choose Merge Down, or press Ctrl+M.

The two layers become one. Any blend modes or opacity on the top layer are applied and baked in. Use Merge Down to clean up as you work - If you are done with a shadow layer that sits over a background, merge them to simplify the stack.

Merge Visible Layers

Merge Visible combines all visible layers into one, while leaving any hidden layers (eye icon turned off) untouched.

1. Hide any layers you want to keep separate by clicking their eye icon.
2. Go to Image > Merge Visible Layers, or press Ctrl+Shift+M.
3. A dialog asks whether to expand or clip to the image. Choose Clipped to image for standard use.

This is useful when you want to merge your main composition into one layer while keeping backup layers hidden. For example: hide your original photo layer, merge all your adjustments into one result layer, and keep the original hidden underneath as a safety copy.

Flatten Image

Flatten Image merges everything - all visible layers - into a single layer and fills any transparent areas with the background color (usually white). Hidden layers are discarded.

1. Go to Image > Flatten Image.

When to use Flatten Image:

• Before exporting as JPEG (JPEG does not support transparency or multiple layers)
• When you are completely done and want to reduce file size
• When sending a final image to someone who does not need the layers

Do not flatten before you are finished. Once you save and close, those layers are gone. Always save a .xcf version first. The relationship between layers and file formats is also relevant when saving transparent backgrounds - PNG preserves transparency, JPEG does not.

Choosing the Right Merge Method

What to Do Before Merging

• Save your .xcf file first. This is the most important step. Once you merge and close, you cannot undo the merge in a future session.
• Check visibility. Make sure layers you want in the merge have their eye icon on, and layers you want to preserve separately are hidden.
• Review blend modes. If a layer uses Multiply or Screen, the effect will be baked in permanently after merging. Check that it looks right before you commit.