I see this is an old question, but I'm going to add another answer anyway since it might be a fix that some people might find helpful.

The real problem here might be that the layer boundary is smaller than the canvas. This is a bit of a guess though.

If this is the case, then it's easily rectified by using Layer > Layer to Image size. This kind of confusion often occurs if a user disables the View > Sow layer boundary option, and therefore has no idea or indication where the layer boundary is. If you switched this off, I suggest you switch it back on. The layer boundary shows as a yellow dashed line.

The reason the Bucket Fill Tool fails to work outside the layer boundary is because in GIMP (unlike Photoshop), layers can be a smaller than the canvas. Quite literally, there are no pixels to edit outside the layer boundary. The fix I suggested rectifies that issue.

I see this is an old question, but I'm going to add another answer anyway since it might be a fix that some people might find helpful.

The real problem here might be that the layer boundary is smaller than the canvas. This is a bit of a guess though.

If this is the case, then it's easily rectified by using Layer > Layer to Image size. This kind of confusion often occurs if a user disables the View > Show layer boundary option, and therefore has no idea or indication where the layer boundary is. If you switched this off, I suggest you switch it back on. The layer boundary shows as a yellow dashed line.

The reason the Bucket Fill Tool fails to work outside the layer boundary is because in GIMP (unlike Photoshop), layers can be a smaller than the canvas. Quite literally, there are no pixels to edit outside the layer boundary. The fix I suggested rectifies that issue.

I see this is an old question, but I'm going to add another answer anyway since it might be a fix that some people might find helpful.

The real problem here might be that the layer boundary is smaller than the canvas. This is a bit of a guess though.

If this is the case, then it's easily rectified by using Layer > Layer to Image size. This kind of confusion often occurs if a user disables the view layer boundary option, and therefore has no idea or indication where the layer boundary is. If you switched this off, I suggest you switch it back on. The layer boundary shows as a dotted yellow line.

The reason the Bucket Fill Tool fails to paint outside the layer boundary is because in GIMP (unlike Photoshop), layers can be a smaller than the canvas. Quite literally, there are no pixels to edit outside the layer boundary. The fix I suggested rectifies that issue.

I see this is an old question, but I'm going to add another answer anyway since it might be a fix that some people might find helpful.

The real problem here might be that the layer boundary is smaller than the canvas. This is a bit of a guess though.

If this is the case, then it's easily rectified by using Layer > Layer to Image size. This kind of confusion often occurs if a user disables the View > Sow layer boundary option, and therefore has no idea or indication where the layer boundary is. If you switched this off, I suggest you switch it back on. The layer boundary shows as a yellow dashed line.

The reason the Bucket Fill Tool fails to work outside the layer boundary is because in GIMP (unlike Photoshop), layers can be a smaller than the canvas. Quite literally, there are no pixels to edit outside the layer boundary. The fix I suggested rectifies that issue.