Sprite Sheet Builder - Free Online Sprite Sheet Maker

What

Sprite Sheet Builder is a free, browser-based sprite sheet maker for packing animation frames into a single transparent sheet and previewing the loop before export. It targets indie game developers and FNF creators who need engine-ready assets for Unity, Godot, Phaser, or Sparrow XML workflows. The tool is positioned around local processing: no sign-up, no watermark, and images stay in the browser.

Features

• Local, private packing: Files are read and packed on the user's device with no account required, keeping images out of upload workflows and avoiding sign-up friction.
• Grid and auto-pack layouts: Grid keeps every cell the same size, while auto-pack fits differently sized sprites more efficiently; both support adjustable padding and spacing, and frames are not rotated.
• Live animation preview: Check the loop at 1–30 FPS before exporting, making timing or ordering issues visible before the sheet is used in an engine.
• Engine-ready exports: Download transparent PNG sheets up to 4096 × 4096, or atlas bundles with JSON for Phaser, Unity import helpers, Godot .tres, and Sparrow XML for FNF.
• Input and mobile handling: Accept PNG, JPG, WebP, GIF, and HEIC; animated GIFs are decoded into editable frames, and mobile users get touch sorting and ZIP downloads.

Helpful Tips

• Use grid when all animation frames share the same dimensions; use auto-pack for mixed-size sprites, but treat the metadata as essential because auto-packed frame positions are irregular.
• Add spacing between frames to reduce neighboring-pixel bleed when the engine filters the texture; padding creates margin around the full atlas, while spacing separates frames inside it.
• Plan around the stated limits: 4096 × 4096 px, 200 frames per export, and 25 MB per uploaded file. For command-line pipelines, polygon packing, or multiple atlases, the page recommends a dedicated packer such as TexturePacker.
• For Unity, choose PNG + JSON and place the included Editor importer in Assets/Editor, then use Tools → Import Sprite Atlas. Export before closing the page, because closing clears the current workspace; mobile browser memory limits still apply.