Free Pixel Art Software

"Multix Personal Utility Vehicle Advertising Campaign" by Rod Hunt

We're big fans of Pixel Art here at The Geek Art Gallery.  A gallery that recently caught our eye inspired us to look into the software available to create our own Pixelated masterpieces.  Here are the most highly recommended utilities available for free.

Alchemy - an open drawing project aimed at exploring how we can sketch, draw, and create on computers in new ways.
OS: Windows, Mac, Linux

Aseprite - Animated sprite editor & pixel art tool." Not many mentions online of this software but it features a nice cozy interface to work with!
OS: Windows, Mac, Linux

GIMP - GNU Image Manipulation Program
OS: Windows, Mac, Linux

Grafx2 - a bitmap paint program inspired by the Amiga programs Deluxe Paint and Brilliance.
OS: Windows, Mac, Linux

GraphicsGale - software especially created for making pixel art, but not at all noob-friendly.  The free version is all you need.  Paid version is about $20.
OS: Windows

iDraw Chara Maker - a graphics program widely used by the game-making community (RPG Maker in particular), which uses palletized graphics, grid snapping, and animation previews. It is very useful for those making graphics for a tile-based game.
OS: Windows

Isoblox - a cross-platform sprite-based pseudo-3D isometric pixel art modeling aid."
OS: Windows, Mac, Linux

Krita - a KDE program for sketching and painting, offering an end–to–end solution for creating digital painting files from scratch by masters.
OS: Windows, Linux

mtPaint - a painting program which Mark Tyler developed from scratch so he could easily create pixel art and manipulate digital photos.
Os: Windows, Linux

MyPaint - a fast and easy open-source graphics application for digital painters.
OS: Windows, Mac, Linux

Paint.NET - an advanced version of Microsoft paint that is easier to use than Microsoft paint.
OS: Windows

Paintbrush - a simple paint program for Mac OS X, reminiscent of Microsoft Paint and Apple’s own now-defunct MacPaint.
OS: Mac

Pencil - a traditional 2D animation softwareOS: Windows, Mac, Linux

Personal Paint - a powerful and intuitive paint, image processing, animation and 24-bit printing package. Employ stunning effects like water-colors, transparencies and stereograms.
OS: Windows

Pickle - a cross-platform pixel editor for creating game animations, tiles and sprite sheets.
OS: Browser based

Pinta - a free, open source drawing/editing program modeled after Paint.NET.
OS: Windows, Mac, Linux

Piq - a free online app for creating pixel art.
OS: Browser based

Piskel - a free online sprite editor. A simple web-based tool for Spriting and Pixel art.
OS: Browser, MacOS, Windows

Pixel - Cross-platform RGB, CMYK and HDR image editing and photo retouching…
OS: Windows, Mac, Linux

Pixel Art Editor - Powerful pixel-art editor with multitouch support.
OS: Android

Pixelation - one of the best pixel editors for the iPhone.
OS: iOS

Pro Motion - a drawing and animation software designed similar to the famous Amiga Deluxe Paint, this software can also be use for pixel art animations.
OS: Windows

RotSprite - a sprite rotation and scaling utility developed by Xenowhirl. It outperforms most professional graphics software (such as Photoshop or Paint Shop Pro) when rotating sprites through an angle other than 90° or one of its multiples. Typically, other graphics editors will apply anti-aliasing or use a primitive nearest-neighbor method when rotating images, which produces results that are ugly or unsuitable for sprites.
OS: Windows

Seashore - an open source image editor for Mac OS X's Cocoa framework.
OS: Mac

Synfig Studio -  a free and open-source 2D animation software, designed as powerful industrial-strength solution for creating film-quality animation using a vector and bitmap artwork.
OS: Windows, Mac, Linux

Tile Studio - a complete development utility for graphics of tile-based games.
OS: Windows

Ultimate Paint - a full-featured 32-bit Windows graphics program for image creation
OS: Windows