Sprite Animator Online — Tags, Timing and Loops for Games
In the Studio an animation is a tag: a run of frames with a direction, a repeat count and its own duration on every frame. Build tags from a sheet, a folder of PNGs or a GIF, watch them loop at the size you will ship, and send the very same timing to a GIF and to your engine.
- Godot 4Verified· Godot 4.7.2
- GIF / APNGDecoded· Pillow
- 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
- .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
What it does
- Tag lanes above the frames: drag across a run to create a tag, rename it in place, drag either end to grow or shrink it.
- Milliseconds on each frame, typed one at a time or applied to a whole selection — a 300 ms anticipation pose between 80 ms steps is ordinary here.
- Direction forward, reverse or ping-pong plus a repeat count, where 0 means loop forever; playback inside the tag obeys both, so what you watch is what the export plays.
- Onion skin (F3) shows the frames before and after with adjustable opacity and tint; the floating preview (F7) plays the loop at 1× to 8× in a window of its own.
- Mirrored copy of the tag: a run-right becomes a run-left with the pixels, the pivot and every box flipped together.
How to do it
- Drop a sheet (and press Apply), a set of numbered frames or a GIF — each GIF delay arrives as that frame's duration.
- On the timeline, drag over the frames of one move to make a tag and name it idle, run or attack.
- Type the durations, choose the direction and repeat, then press Enter to watch it and use , and . to step.
- Export one GIF per tag, or open Pack & Export for Godot 4, Unity 6, Phaser or Aseprite JSON.
Where each animation setting ends up
The same tag, as each export writes it.
| Setting | Godot 4 SpriteFrames | Unity 6 clip | Phaser anims.json | Aseprite JSON | GIF |
|---|---|---|---|---|---|
| Tag name | Animation name | One AnimationClip per tag | Animation key | frameTags name | One file per tag |
| Frame duration (ms) | speed = tag fps; duration = ms ÷ (1000 ÷ fps) | Each frame keyed at its own time | duration in ms on each frame | duration in ms on each frame | Delay in 1/100 s, 2 at least |
| Direction | Reverse and ping-pong written out as frame order | Reverse and ping-pong written out as frame order | Reverse written out; ping-pong = yoyo | direction: forward, reverse or pingpong | Frames in playback order |
| Repeat (0 = forever) | loop on only for 0 | Loop Time on only for 0 | repeat −1 for forever; n plays = repeat n−1 | repeat count in frameTags | Loop count 0 for forever, n−1 for n plays, none for a single play |
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
Why a duration per frame instead of one frame rate?
Because animation holds some poses longer than others. Engines that think in one rate still get the right timing: Godot 4 receives the tag's fps as the speed and each frame's share of it as a relative duration (250 ms at 12 fps becomes 3.0).
What does ping-pong become in Godot or Unity?
Godot's SpriteFrames has no ping-pong setting, so the Godot and Unity exports both write the order out: frames 1, 2, 3, 2 and so on. Reverse is written the same way. Phaser gets yoyo instead, and Aseprite JSON keeps the direction in frameTags.
Why is my fastest GIF frame slower than I set?
GIF delays count in hundredths of a second, and browsers and Discord treat 0 or 1 as 10. The writer therefore never goes below 2 (20 ms) and tells you which frames it rounded. APNG stores milliseconds if you need exact timing.
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).