Aseprite Viewer Online — Open .aseprite and .ase Files

Someone sent you an .aseprite file, or an asset pack ships its sources that way, and Aseprite is not installed on this machine. Drop the file here: it is parsed inside this browser tab, every frame is composited the way Aseprite's own PNG export draws it, and the tags play on the Timeline.

An .aseprite or .ase file is Aseprite's own binary document, not an image: it stores every frame with its duration in milliseconds, the layers with blend mode and opacity, the cels, tags, slices and palette. Browsers and image viewers cannot open it. Drop it here: Nerulio parses it inside this tab, composites each frame the way Aseprite's PNG export does (checked on 231 real files against Aseprite 1.3.18.6), plays the tags, and can save a PNG sheet with Aseprite JSON, a GIF or APNG per tag, or a new .aseprite. Nothing is uploaded.

Drop a sprite sheet, numbered frames, a GIF / APNG or an .aseprite file

Open the empty Studio

Runs in your browser. Files are not uploaded.

The real Studio with a CC0 asset (Nerulio).

Exports to

Aseprite JSONVerified· Phaser load.aseprite · PixiJS 8.21
.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
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 is inside an .aseprite file

The format is documented by the Aseprite project. A 128-byte header holds the magic number 0xA5E0, the canvas size and the colour depth: 32 bits per pixel is RGBA, 16 is grayscale with alpha, 8 is indexed, where every pixel is a palette index and one index can be transparent. Then come the frames. Each frame has a 16-byte header with its own duration in milliseconds, followed by chunks: layers (in the first frame), cels, palette, tags, slices, user data and, for tilemap layers, tilesets.

What you see in Aseprite is not stored anywhere as a finished picture. A frame is built by drawing the visible layers from bottom to top: each cel (one layer's pixels at one frame, at its own x and y) with the layer opacity times the cel opacity, mixed by one of 19 blend modes from Normal to Divide. A cel can be linked, reusing another frame's pixels, and it can carry a z-index that moves it above or below other layers for that frame only. A viewer that shows the first layer, or ignores blend modes, shows a picture Aseprite would never export.

Nerulio keeps the layers only when drawing them again with its own compositor gives exactly the pixels Aseprite renders; otherwise it shows the flattened frames and names the reason. On the 231-file test corpus 222 files stayed layered and 9 were flattened: 5 whose group composition differs and 4 that reorder layers with cel z-index. The frames are identical either way.

Cel: One layer's pixels at one frame, with its own position and opacity. A linked cel points at the cel of another frame instead of storing pixels.
Tag: A named frame range (from–to) with a direction (forward, reverse, ping-pong, ping-pong reverse) and a repeat count. Repeat 0 means “not specified”: endless in Aseprite's editor, once on export.
Slice: A named rectangle, optionally with a 9-patch centre or a pivot point. Its keys are per frame: a key holds from its frame until the next key.
Colour mode: RGBA, grayscale or indexed. In an indexed file the palette can change during the animation and one index is the transparent colour.

Example: reading a small character file

What the Import panel and the Timeline show for a 32 × 32 RGBA file with three layers and three tags, and the timing that follows from it:

hero.aseprite  32 × 32 px · RGBA · 16 frames · 3 layers · 3 tags · 2 slices
layers  outline  Normal    255
        shadow   Multiply  128   (drawn at 128/255 ≈ 50 % over the layers below)
        body     Normal    255
tags    idle    0–3    4 × 125 ms                    forward ∞   one cycle 500 ms
        walk    4–9    6 × 100 ms                    forward ∞   one cycle 600 ms
        attack  10–15  100,100,100,100,150,250 ms    forward ×1  plays once, 800 ms
slices  pivot  point (16, 31) on every frame  → frame pivot, confidence high (name)
        hit    20 × 8 from frame 12           → hit box, confidence medium (name)

Set idle to ping-pong and one cycle becomes 0-1-2-3-2-1: six steps, 750 ms. The two slice guesses are decisions in the Import panel; click one to turn hit into a hurt box or to ignore it.

What it does

Layers with all 19 blend modes, layer and cel opacity, groups, hidden and reference layers, cel z-index and linked cels, composited like Aseprite's export.
RGBA, grayscale and indexed sprites, palettes that change per frame and the transparent index; tilemap layers drawn tile by tile with their flips.
Tags with their direction (forward, reverse, ping-pong, ping-pong reverse) and repeat count, and each frame's own duration in milliseconds.
Slices become Studio data: a slice named pivot, origin or anchor sets the pivot, other slices become hit, hurt, interact or custom boxes guessed from their names, and 9-patch slices keep their centre.

How to do it

Drop the .aseprite or .ase file anywhere on the Studio.
Read the Import panel: whether the layers were kept or flattened and why, and how each slice was mapped, each with a confidence.
Press Enter to play the current tag; step with , and . and turn on onion skin (F3) or the floating preview (F7, up to 8×).
Click a frame on the Timeline to see its duration, pivot and boxes in the Frame panel.
To keep a copy in another format, open Pack & Export (PNG sheet with Aseprite JSON, a GIF or APNG per tag) or use Sprite › Export .aseprite… for a file Aseprite opens.

What you can save from the viewer

File	What it is for
`hero.png + hero.json`	Pack & Export › Aseprite JSON (hash or array): one packed sheet with `frames`, `meta.frameTags` and `meta.slices`, in the layout of Aseprite's own sprite sheet export. See Aseprite to sprite sheet.
`hero_idle.gif …`	Pack & Export › Animated GIF: one file per tag, delays rounded to 1/100 s. See Aseprite to GIF.
`hero_idle.png …`	Pack & Export › APNG: one animated PNG per tag, every pixel and millisecond exact.
`hero.aseprite`	Sprite › Export .aseprite…: a new file Aseprite opens, with layers, tags, durations and slices. The original you dropped is never changed.

Check the result

Import panel, layer decision: “layered” means the layer rows reproduce Aseprite's render on every frame; “flattened” gives the reason and the first frame that differed.
Step through a tag with , and . and read each frame's duration in the Frame panel; the sum is one cycle (walk: 6 × 100 ms = 600 ms).
Play the tag with Enter: a repeat of ×1 stops on its last frame, ∞ keeps looping.

What the viewer reads from an .aseprite file

In the file	What you see in the Studio	Checked against
Layers, groups, blend modes, opacity	Layer rows on the Timeline; flattened with a reason when they cannot be rebuilt exactly	Aseprite 1.3.18.6 frame exports: 231/231 files pixel-exact
Tags and frame durations	Tag lanes over the frames, milliseconds per frame; playback follows direction and repeat	Aseprite's scripting view: 231/231 files identical
Slices: pivot, plain, 9-patch	Frame pivot; hit / hurt / interact / custom boxes; 9-slice borders	31 corpus files with slices
Tilemap layers and tilesets	Drawn into each frame tile by tile, flips included	23 corpus files with tilemaps
Indexed and grayscale colour	Full colour, composited by index as Aseprite's PNG export does	54 indexed and 13 grayscale corpus files

ICC colour profiles are read and kept but not applied, which is also what Aseprite's PNG export does.

Troubleshooting

Symptom	Likely cause	How to check	Fix
“Not an Aseprite file” or “ends early”	The header does not start with Aseprite's magic number `0xA5E0` (another program's `.ase` file), or the download was cut off	Compare the file size with the source; open it in Aseprite if you can	Get the complete original file; `.ase` files made by other programs cannot be read here
Layers show as one “Flattened” layer	The file uses cel z-index or group composition that cannot be rebuilt exactly from separate layers	The layer decision in the Import panel names the reason and the frame	The frames are still exact; to work on single layers, edit the layer structure in Aseprite and import again
A layer you see in Aseprite is not in the frames	It is hidden (eye closed) or a reference layer; Aseprite's export leaves both out, and so does Nerulio	The layer list in the Import panel, or the eye icon in Aseprite	Make the layer visible in Aseprite and save; reference layers are never part of the frames
A slice became the wrong kind of box, or there is no pivot	Box types are guessed from slice names (hit, hurt …); the pivot is the slice named pivot, origin or anchor, else the first slice that has a pivot point	Import panel: each slice decision with its confidence	Pick the right type (hit, hurt, interact, custom) or ignore it; frames without a pivot slice use the bottom centre
Colours differ slightly from Aseprite's canvas	The file has an ICC colour profile; it is kept but not applied, as in Aseprite's PNG export	Aseprite's colour profile setting	Compare with a PNG exported from Aseprite rather than with the editor canvas

Other ways to do it

Option	When it is the better choice
Aseprite itself	You want to change the file with every Aseprite feature (layers, groups, tilemaps, scripts). Opening here is read-only.
Aseprite's command line (`aseprite -b`)	You have Aseprite and want output from scripts: `--sheet`, `--data`, `--list-tags`, `--list-slices`, and `--save-as` with `{tag}` for one GIF per tag.
A browser alternative to Aseprite	You want to draw and animate rather than only open a file.

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

Group layers are not kept as groups: each leaf layer becomes a row named with its group path, such as arms/left.
Reference layers are skipped, as in Aseprite's export.
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.

Versions and sources

The reader follows the Aseprite file format specification and was checked on 231 real .aseprite files: each was imported, written back with Nerulio's writer and opened in Aseprite 1.3.18.6 without a warning, with the same tags (231/231), durations (231/231) and pixels (231/231). The layer decisions come from the same corpus: 222 layered, 9 flattened. What this page says about the format follows the specification and the Aseprite documentation.

Official documentation used

Questions

Can I convert .aseprite to PNG without Aseprite?

Yes. Pack & Export draws the frames onto PNG atlas pages with an exact PNG writer (an indexed PNG when a page has 256 colours or fewer), next to the data file of the target you pick. For a moving picture, APNG keeps every pixel of each tag.

Why were my layers flattened?

Layers are kept only when composing them again gives exactly the pixels of the original. On the 231-file test corpus that held for 222 files; the other 9 (5 where group composition differs, 4 that use cel z-index) were flattened with the reason in the Import panel. The frames look the same either way.

Can opening the file here change my original?

No. The browser only reads it. A new .aseprite is written only when you choose Sprite › Export .aseprite…; files re-written that way were opened in real Aseprite 1.3.18.6, 231 of 231 without a warning, with the same tags, durations and pixels.

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).