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.

Tags and frame durations disappear when the packer never receives them: PNG frames carry no tags or timing, and an Aseprite JSON exported without Tags in its Meta options (or without --list-tags on the command line) has no meta.frameTags. Check what went into the packer first. Packing the .aseprite file itself in Nerulio, or its JSON with frameTags, keeps every tag, direction, repeat, per-frame duration and pivot, and writes them in each engine's own form; where a format has no field for them, the export note says so.

Drop frame images, a GIF or an .aseprite file to pack

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Studio Pack & Export: CC0 ninja frames packed on one page and the list of all 18 export formats, each with its own Export button — The real Studio with a CC0 asset (OpenGameArt).

Exports to

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

Where tags get lost

An Aseprite tag is metadata: a name, a from–to range, a direction and a repeat count, stored in the .aseprite file next to each frame's duration. As soon as the frames leave Aseprite as PNG files, that metadata is gone; a packer can only guess animations from file names (walk_01, walk_02 → walk) and has no durations, direction or repeat to write.

The JSON route keeps them only if you asked for them. Aseprite writes meta.frameTags when Tags is ticked in the export's Meta options, or with --list-tags together with --data on the command line. Without it the JSON still has every frame and its duration, but no animation names, and a loader such as Phaser's createFromAseprite has nothing to create.

The third place is the engine format. Some formats have no field for animations at all (a Spine/libGDX atlas lists regions only), some keep one speed per animation (Defold), and PixiJS reads animation names but no per-frame time. Nerulio writes what each format can hold and bakes direction into frame order where there is no field for it. It cannot recreate tags that are in none of its inputs: from bare PNG frames it groups by name, and you rebuild the rest on the Timeline.

frameTags: The meta array of an Aseprite JSON holding each tag's name, range and direction.
--list-tags: The Aseprite CLI option that adds the tags to the --data JSON.
Contiguous run: A tag's frames must be consecutive, because a tag is a from–to range.
Playback order: The frame sequence of one cycle with reverse or ping-pong written out.

Example: the same file exported with and without tags

aseprite -b hero.aseprite --sheet hero.png --data hero.json
  → "frames": { "hero 0.aseprite": {…, "duration": 125}, … "hero 15.aseprite": {…} }
  → "meta": { "image": "hero.png", … }                      no "frameTags"
  → Nerulio import: names differ only by number → 1 animation "hero", 16 frames

aseprite -b hero.aseprite --sheet hero.png --data hero.json --list-tags
  → "meta": { …, "frameTags": [ { "name": "idle", "from": 0, "to": 3, "direction": "forward" }, … ] }
  → Nerulio import: idle 0–3, walk 4–9, attack 10–15, durations kept

hero.aseprite dropped directly → the same 3 tags + repeat counts + pivot and box slices

In both JSON cases the per-frame duration survives; only the grouping into tags depends on frameTags. The key names follow the filename format of the export ({title}, {frame} …), so yours may differ.

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.

Check the result

aseprite -b hero.aseprite --list-tags prints the tag names; the Timeline in Nerulio should show the same tag lanes before you pack.
After export, count the animations in the engine file (Phaser .anims.json, PixiJS animations, Godot SpriteFrames panel) against that list.
Pick one tag and add up its frame times in the engine file; the sum should equal the tag's cycle in Aseprite (walk: 6 × 100 ms = 600 ms).
Read the export notes: repeated entries (a frame shared by two tags) and anything the target cannot store are listed there.

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

Troubleshooting

Symptom	Likely cause	How to check	Fix
No animations after packing PNG frames	PNG files carry no tags or timing; the packer only saw file names	Your packer input is a folder of PNGs	Pack the `.aseprite` file (or its JSON with `frameTags`) instead; see Aseprite to sprite sheet
The Aseprite JSON has no `frameTags`	Exported without Tags in the Meta options, or without `--list-tags` on the command line	Search the JSON for `frameTags`	Export again with Tags ticked or `--list-tags`, or drop the `.aseprite` itself
Every frame ended up in one animation	No `frameTags`, so Nerulio grouped by name, and the frame names differ only by their number (`hero 0`, `hero 1` …)	The Import panel's animations decision says the frames were grouped by name	Re-export with tags, or drag tags over the frames on the Timeline
A tag plays the wrong frames	A tool re-sorted the frames (for example `hero 10` before `hero 2`), so the `from`–`to` ranges point at other frames	Compare the frame order in `frames` with the tag ranges	Keep the original order; Nerulio sorts numbers naturally and keeps each tag one run, repeating shared frames
Tags survive but all frames play at the same speed	The target keeps one speed per animation (Defold), or the engine code ignores the stored times (PixiJS without `durationsMs`)	The target's row in the table above; your animation code	Use a target that stores per-frame time, or pass the times in code as in Aseprite JSON to PixiJS
A ping-pong or play-three-times tag loops normally	The format has no field for direction or repeat: Godot keeps a loop flag, PixiJS only `loop`	Direction is written out as frame order; the repeat count is gone	Handle the count in code (for example on `animation_finished` in Godot)
The atlas has no animations at all	Spine/libGDX `.atlas` and CSS sprites list regions only	Open the file: no animation section	Use an engine target (Godot, Unity, Phaser, PixiJS) or Aseprite JSON

Other ways to do it

Option	When it is the better choice
Aseprite's own sheet export with `--list-tags`	You only need Aseprite JSON for Phaser and have Aseprite installed.
A free texture packer in the browser	You pack many sprites into one atlas and still want Aseprite tags to reach the engine.

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

Tags that exist in no input (bare PNG frames) cannot be recovered, only rebuilt by hand.
GameMaker strip timing is written but UNVERIFIED in GameMaker itself.
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.

Versions and sources

The .aseprite round trip kept tags and durations on all 231 corpus files (reopened in Aseprite 1.3.18.6). Per-target results are from engine runs: Godot 4.7.2, Unity 6000.5.3f1, Phaser 3.90 and 4.2, PixiJS 8.21, Defold 1.13.1. The Aseprite export options and Phaser's requirements follow their documentation.

Official documentation used

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).