[5] In 1995, Spencer Kimball and Peter Mattis began developing GIMP—originally named General Image Manipulation Program—as a semester-long project at the University of California, Berkeley for the eXperimental Computing Facility.

[6] The acronym was coined first, with the letter G being added to -IMP as a reference to "the gimp" in the scene from the 1994 film Pulp Fiction.

After a source code release, installers and packages are made for different operating systems by parties who might not be in contact with the maintainers of GIMP.

The healing brush and perspective clone tools and Ruby bindings were created as part of the 2006 GSoC and can be used in version 2.8.0 of GIMP, although there were three other projects that were completed and are later available in a stable version of GIMP; those projects being Vector Layers (end 2008 in 2.8 and master),[20] and a JPEG 2000 plug-in (mid 2009 in 2.8 and master).

[25][26] Increase of possible threads to 64 is also an important point for modern parallel execution in actual AMD Ryzen and Intel Xeon processors.

[33] The current version of GIMP works with numerous operating systems, including Linux, macOS and Windows.

[45] Lifewire reviewed GIMP favorably in March 2019, writing that "[f]or those who have never experienced Photoshop, GIMP is simply a very powerful image manipulation program," and "[i]f you're willing to invest some time learning it, it can be a very good graphics tool.

"[46] GIMP's fitness for use in professional environments is regularly reviewed; it is often compared to and suggested as a possible replacement for Adobe Photoshop.

Courtney explains GIMP is a powerful tool, fully capable of large professional projects, such as video games.

[49] The single-window mode introduced in GIMP 2.8 was reviewed in 2012 by Ryan Paul of Ars Technica, who noted that it made the user experience feel "more streamlined and less cluttered".

[50] Michael Burns, writing for Macworld in 2014, described the single-window interface of GIMP 2.8.10 as a "big improvement".

[51] In his review of GIMP for ExtremeTech in October 2013, David Cardinal noted that GIMP's reputation of being hard to use and lacking features has "changed dramatically over the last couple years", and that it was "no longer a crippled alternative to Photoshop".

Cardinal favorably described the UFRaw converter for raw images used with GIMP, noting that it still "requires some patience to figure out how to use those more advanced capabilities".

[53] Tools used to perform image editing can be accessed via the toolbox, through menus and dialogue windows.

They include filters and brushes, as well as transformation, selection, layer and masking tools.

GIMP's developers have asserted that it has, or at least aspire to it having, similar functionality to Photoshop, but has a different user interface.

[54] Also, as of 2024 and version 2.10, a fundamental and essential difference between GIMP, on one hand, and major commercial software like Photoshop and Serif Affinity Photo, on the other, is that very few of GIMP's editing operations occur as non-destructive edits, unlike the main commercial software.

GIMP also supports a quick mask mode where a user can use a brush to paint the area of a selection.

Users can use paths to create complex selections, including around natural curves.

These color transitions can be applied to large regions or smaller custom path selections.

GIMP also provides "smart" tools that use a more complex algorithm to do things that otherwise would be time-consuming or impossible.

The Unsharp Mask tool is considered to give more targeted results for photographs than a normal sharpening filter.

[72] When GEGL is fully integrated, GIMP will have a higher color bit depth and better non-destructive work-flow.

[74][75] GIMP supports importing and exporting with a large number of different file formats.

Import and export capability can be extended to additional file formats by means of plug-ins.