Keep Aseprite Tags When Packing — Durations and Pivots Too
Export PNG frames from Aseprite, pack them in a separate packer, and the tags, per-frame durations and slices usually stay behind: a packer that builds animations from numbered file names never sees them. Pack the .aseprite file itself and they reach the engine file.
- Godot 4Verified· Godot 4.7.2
- Phaser 3 / 4Verified· Phaser 3.90 + 4.2
- Aseprite JSONVerified· Phaser load.aseprite · PixiJS 8.21
- Unity 6Verified· Unity 6000.5.3f1
- PixiJS 8Verified· PixiJS 8.21
- .asepriteVerified· Aseprite 1.3.18
- 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
- Reads .aseprite and .ase directly: tags with direction (forward, reverse, ping-pong) and repeat count, each frame's duration, and slices as pivots, hit/hurt boxes and 9-slice.
- Frames of one tag stay one contiguous run, so Aseprite JSON's frameTags from..to still point at the right frames after packing.
- Every target gets the data in its own form: Godot relative durations, one Unity AnimationClip per tag, a Phaser anims.json, a PixiJS animations map, Aseprite JSON frameTags.
- Where a format has no field for direction or repeat, the playback order is written out instead, so ping-pong still plays as ping-pong.
- The round trip holds: 231 corpus files imported, written back as .aseprite and opened in Aseprite 1.3.18.6 with tags, durations and pixels intact on all 231.
How to do it
- Drop the .aseprite file into the Studio.
- Check the tag lanes and durations on the Timeline; rename or add tags there if needed.
- Open Pack & Export and choose your target.
- Export: each tag arrives as an animation with its own frame timing.
What each target keeps from the .aseprite file
| Target | Tags | Durations | Direction / repeat | Pivots | Boxes |
|---|---|---|---|---|---|
| Godot 4 | One SpriteFrames animation per tag | Relative to the tag's fps (Godot's rule) | Written as playback order, loop flag | Node offset from the first frame; all pivots in metadata | In the resource metadata "nerulio", not as nodes |
| Unity 6 | One AnimationClip per tag | Each key at its frame's own time | Playback order, loop | Pivot per sprite rect | Not written |
| Phaser 3 / 4 | One animation per tag in .anims.json | ms per frame | Ping-pong as yoyo, reverse baked, repeat count | pivot per frame | Not written |
| PixiJS 8 | animations map | ms per step in meta.nerulio | Playback order | anchor per frame | Not written |
| Aseprite JSON | meta.frameTags (contiguous from..to) | duration per frame | direction and repeat fields | A "pivot" slice | Rectangle boxes as slices |
| Generic JSON | Tags and playback | ms per frame | direction, loop and the playback order | pivotPx per frame | Boxes and collision polygons |
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
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. Packer head-to-head on 5 real frame sets (CodeAndWeb free web packer, GAPTools, free-tex-packer): smallest sheet on all 5 with rotation allowed, 4 of 5 without; every frame restored pixel-exact.
Limits
- Polygon (mesh) packing is not offered: none of the verified engines draws a mesh atlas from exported data.
- GameMaker strips are UNVERIFIED in GameMaker itself.
- Scale variants (@0.5x–@4x) use nearest-neighbour only.
- Trimmed Starling XML is drawn wrongly by Phaser 3.90; use the "Sparrow XML (Phaser 3)" preset there.
Questions
Why did my tags disappear after packing?
PNG frames carry no tags or timing. A packer can group walk_01, walk_02 into "walk" by name, but it has no durations, direction or repeat to write. Packing the .aseprite (or Aseprite's JSON with frameTags) keeps them.
I already exported Aseprite JSON. Can I use that?
Yes. Drop the JSON (hash or array) together with its PNG; tags come from frameTags and each frame keeps its duration.
What happens to my layers?
Layers are kept when they compose exactly; otherwise the file is flattened and the reason is shown. Packing always uses the composed frame.
Does any target lose timing?
Defold keeps one fps per animation, so frames with their own durations play at the fps of their tag. GameMaker strips get a speed plus the ms of each frame in gamemaker.json, and that output is UNVERIFIED in GameMaker.
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).