If you came looking for free-tex-packer.com and found it offline — the tool isn't gone. This is a maintained build of the same open-source Free Texture Packer, running free in your browser.
Open Free Texture Packer →Free Texture Packer is a free, open-source sprite sheet generator. It packs a folder of individual images into one or more texture atlases for 2D games and websites — with rotation, trimming, multipacking and a range of export formats including Phaser, PixiJS, Godot, cocos2d, Unity, Spine, Starling, Egret and plain CSS/JSON/XML. It runs entirely in your browser; your images are not uploaded anywhere.
The original site at free-tex-packer.com went offline. The project itself is open source
and MIT-licensed, so the tool lives on: this site hosts a maintained build of it at
free-tex-packer.org so the tool — and the links pointing to it — keep working.