Sprite Sheet to Aseprite — Cut, Tag and Save .aseprite
To rework a downloaded or old sprite sheet in Aseprite you want frames and tags, not one big picture. Drop the PNG here: the Studio measures the grid (margin and spacing included) or finds each sprite as an island, removes a flat background colour, makes each row a tag, and writes one .aseprite file with the timing, the pivot and the hitboxes as slices.
- .asepriteVerified· Aseprite 1.3.18
- Godot 4Verified· Godot 4.7.2
- Unity 6Verified· Unity 6000.5.3f1
- Phaser 3 / 4Verified· Phaser 3.90 + 4.2
- PixiJS 8Verified· PixiJS 8.21
- Aseprite JSONVerified· Phaser load.aseprite · PixiJS 8.21
- Spine / libGDXVerified· spine-canvas 4.2
- Starling / Sparrow XMLVerified· Phaser 4.2
- LÖVEVerified· LÖVE 11.5
- DefoldBuilt· Defold bob.jar 1.13.1
- GameMakerUNVERIFIED
- CSS spritesVerified· Chromium
- GIF / APNGDecoded· Pillow
What it does
- Grid measured from the pixels with cell size, margin, spacing and a confidence; islands mode for irregular sheets keeps small effect pieces with their sprite and marks pieces it cannot place in red.
- Magenta or any flat background colour keyed to transparency; the untouched original is kept so the change can be undone.
- One animation per row to start with; rename, resize or drag out new tags on the Timeline, each with direction (forward, reverse, ping-pong) and repeat.
- Durations per frame or for a whole tag at once (Set all to fps), a pivot (P) and rectangle boxes (B) typed hit, hurt, interact or your own word.
- Sprite › Export .aseprite… writes the frames, tags, durations in whole milliseconds, a pivot slice and one slice per box.
How to do it
- Drop the sprite sheet PNG.
- Check the grid or islands guess and the background colour, choose an alternative if one is wrong, then press Apply (one undo step).
- On the Timeline, make one tag per animation and set its direction and repeat.
- Add timing, a pivot and hitboxes where you need them.
- Choose Sprite › Export .aseprite… and open the file in Aseprite.
What goes into the .aseprite file
| From the Studio | Written in the .aseprite as | Notes |
|---|---|---|
| Frames cut from the sheet | one frame each on a canvas the size of the largest frame | each frame keeps its own offset |
| Tags | tags with from..to, direction and repeat | a backwards run is written as reverse |
| Frame durations | a duration per frame in whole milliseconds | untouched frames stay at 100 ms, Aseprite's own default |
| Pivot | a slice named pivot with its pivot point | left out while every frame keeps the default bottom-centre pivot |
| Rectangle boxes | one slice per box type (hit, hurt, hit2 …), keyed where the box changes | circles and polygons are skipped |
| Layers | the asset's layers with opacity and blend mode | a cut sheet has one layer |
Engine exports and how each was checked
"Verified" means the exported files were loaded by the real engine or tool on real CC0 assets and the result was compared with the source. Anything that was not loaded is labelled as such.
| Target | Files | Check |
|---|---|---|
| Godot 4 | .tres SpriteFrames · .tscn AnimatedSprite2D · .png.import | Verified Godot 4.7.2Loaded by Godot; every animation frame drawn and compared with the source file. The scene uses Nearest filtering; rotation is never used. |
| Unity 6 | .unity.json · Editor/NerulioSpriteImporter.cs · AnimationClip | Verified Unity 6000.5.3f1Batch mode: sprite rects, pivots, pixels, clip keys and durations checked. |
| Phaser 3 / 4 | atlas JSON (multiatlas) · .anims.json | Verified Phaser 3.90 + 4.2Frames and animations drawn by both versions. |
| PixiJS 8 | spritesheet JSON · animations · anchor · meta.scale | Verified PixiJS 8.21Rotated and multi-page atlases included. |
| Aseprite JSON | hash / array · frameTags · slices | Verified Phaser load.aseprite · PixiJS 8.21Tags keep their direction and repeat count. |
| .aseprite | layers · tags · durations · slices | Verified Aseprite 1.3.18Opened and rendered by the Aseprite command line. |
| Spine / libGDX | .atlas | Verified spine-canvas 4.2Every region drawn by the Spine runtime, rotated and trimmed; libGDX itself was not run. |
| Starling / Sparrow XML | XML per page | Verified Phaser 4.2Phaser 3.90 draws trimmed XML frames wrongly (its own bug); the "Sparrow XML (Phaser 3)" preset turns trim off and passes in 3.90 and 4.2. |
| LÖVE | Lua quads · nerulio_atlas.lua · main.lua | Verified LÖVE 11.5Every frame drawn and every animation stepped through the shipped helper. |
| Defold | .atlas · .tilesource | Built Defold bob.jar 1.13.1Built by Defold's command-line builder; the built texture's UVs were read back. |
| GameMaker | spr_<name>_stripN.png · gamemaker.json | UNVERIFIEDNot loaded in GameMaker (no headless GameMaker). The strips are cut the way its strip importer cuts them. |
| CSS sprites | .css · preview .html | Verified ChromiumEvery class drawn from the shipped stylesheet. |
| GIF / APNG | one file per animation | Decoded PillowEvery frame and delay decoded again after export; APNG is exact. |
Evidence
GIF decoder: 408 of 408 frames identical to Pillow on 29 real GIFs; APNG 132 of 132 on 16 files. .aseprite: 231 corpus files imported, re-written and reopened in Aseprite 1.3.18 with the same tags, durations and pixels (231/231). Exports: 49 runs in the real engines on real CC0 assets, 47 pass — the 2 failures are Phaser 3.90's trimmed-XML bug, which the Phaser 3 preset avoids.
Limits
- A grid or island guess is a preview with a confidence; nothing is cut until you press Apply, and every choice has one-click alternatives.
- .aseprite files whose layers do not compose exactly (e.g. group opacity) are imported flattened, and the Import panel says why.
- Rotated frames in an imported atlas stay rotated; their export is UNVERIFIED.
- Images up to 32,768 px per side (268 million pixels), subject to your browser's memory.
Questions
Will Aseprite open the file without complaints?
The writer was checked on 231 real .aseprite files imported into the Studio and written back: real Aseprite 1.3.18.6 opened all of them without a warning, with the same tags, durations and pixels. A sheet you cut here goes through that same writer.
What happens to circle and polygon hitboxes?
Aseprite slices are rectangles, so only rectangle boxes are written; circles and polygons are skipped, and the export message names them. Collision polygons stay in the project and in the Godot and Generic JSON exports.
Can a tag skip frames?
An Aseprite tag is a from..to range. A tag whose frames are consecutive on the Timeline, forwards or backwards, is written; one with gaps is left out and named rather than bent into a wrong range. Drag the frames into order and export again.
Is it free, and do I need an account?
Everything on these pages is free and works without an account. There is no watermark and no export that is held back.
Are my sprites uploaded?
No. The Studio decodes, packs and exports in this browser tab. Projects are autosaved in the browser (IndexedDB) and can be saved as a .nerulio file.
Does it need Aseprite or an engine plugin installed?
No. .aseprite files are read and written in the browser, and each engine bundle carries what that engine needs (for Godot, the import settings and scene; for Unity and the Godot TileSet, a small editor script).