This shows a typical image editing window in the GIMP (this is version 1.2, more recent versions will have a set of menus at the top of the image window) Right-click, File, Save is used to save the image. A filetype can be selected (png, jpeg, etc.) from the dropdown list, but the default action is to use whatever extension was typed (specifying "image.jpg" causes it to save a JPEG file)

After the filename is specified, there is an additional dialog box specific to each filetype. For example, a JPEG image will ask you for the compression level, and it can be useful to adjust this until the image is a reasonable filesize.

Image formats Supported by GIMP

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as of GIMP 2.2.13

Significant file formats
File Format Extension(s) Description
XCF .xcf/
.xcf.gz/.gz/.xcfgz/ .xcf.bz2/.bz2/.xcfbz2/ .gbr/.gih/.pat
GIMP's native format which will preserve all image data, including layer, the current selection, channels, transparency, paths and guides, but it doesn't save undo history. XCF images take up a lot of space, and are not supported by most image viewers, which is why XCF is only good for saving images for future editing (not for image exchange). There is also an option to compress the XCF by using either gzip (using xcf.gz/gz/xcfgz extension) or bzip2 (using xcf.bz2/bz2/xcfbz2 extension) compression. GIMP's other native formats include GIMP Brush (.gbr), GIMP Animated Brush (.gih), and GIMP Pattern (.pat).
BMP .bmp/.dib Bitmap is an uncompressed image format, which is the internal image format for Windows and OS/2 Graphic Subsystem.
GIF .gif Graphic Interchange Format is often used for screenshots and computer graphics. It is lossless if the image has under 256 color or otherwise it become lossy. It allows transparent mask, which means a pixel can only be fully transparent or fully opaque, and not partially transparent.
HTML .htm/.html Hypertext Markup Language. GIMP will save in HTML as a HTML page that contains a table containing the image.
ICO .ico Icon Image File Format is Windows' image format for icons.
JPEG .jpg/.jpeg/.jpe Joint Photographic Experts Group is typically used for photographs. It uses lossy compression that results in a loss of detail, commonly called artifacts. The artifacts are usually most noticeable on images that have sharp edges, while less noticeable on photographs, which have many smooth gradients.
PNG .png Portable Network Graphic is often used for screenshots and computer graphics. It uses lossless compression. It allows full alpha transparency.
PNM .pnm/.ppm/.pbm/ .pgm/.pam Portable Pixmap. PNM (Portable Any Map, a shorthand for ppm, pbm, and pgm format), PPM (Portable Pixel Map), .pbm (Portable Bit Map), .pgm (Portable Gray Map) and .pam (Portable Arbitrary Map).
PS and EPS .ps/.eps Postscript Document and Encapsulated Postscript
PSD .psd Photoshop Document, the native format of another popular graphic editing software, Adobe Photoshop.
TGA .tga Truevision Graphics Adapter, Targa's native image format.
TIFF .tif/.tiff Tagged Image File Format
XBM .xbm X Bitmap 2-bit, Monochrome Bitmap for X Window System
XPM .xpm X Pixelmap Color Bitmap for X Window System



Other less popular image format also supported by GIMP:

Extension(s) Description
.pix/.matte/.mask/.alpha/.als Alias/Wafefront Pix Image
.fli/.flc Autodesk FLIC Animation
.c/.h C/C Header Sourcefile Format
.dcm/.dicom Digital Imaging and Communications in Medicine Image
.fit/.fits Flexible Image Transport System
.cel KISS Cel
.sgi/.rgb/.bw/.icon Silicon Graphic IRIS Image
.im1/.im8/.im24/im32/.ras/.rs SUN Rasterfile Image
.pcx/.pcc ZSoft PCX Image
.xwd X Windows Dump



Other file formats that GIMP can only read, but not write:

Extension(s) Description
.g3 G3 Fax Image
.wmf/.apm Microsoft WMF File
.psp/.tub Paintshop Pro
.pdf Printable Document File
.svg Scalable Vector Graphic
.fit/.fits Flexible Image Transport System

GIF images

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The Unisys patent has now expired and in recent versions of the GIMP you should be able to save compressed GIF images using GIMP.

If your version will not save GIF files and it is updated, you may want to update the corresponding image libraries for GIF.

Colours · Saving as JPEG

Colours · GIMP · Saving as JPEG