Open any ICO file online and view every icon size inside it - zoom to the pixel, preview it in a browser tab and on Windows, and find out why Windows won't open it. Need a new icon? PNG to ICO makes one in seconds, and ICO to PNG goes the other way.
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Shortcuts: Ctrl + O open, Ctrl + V paste a file, arrow keys move the pixel cursor in Inspect, Esc leaves full screen.
Size, bit depth, PNG or BMP, bytes, offset, palette, colours and how transparency is stored - for each image in the file.
Zoom up to 32× with a pixel grid. Hover any pixel for its position and exact RGBA value, click to pin and copy it.
Light and dark browser tabs, a search result, the taskbar, the desktop and Explorer - with the layer Windows really picks at each scaling.
Plain-English pass, warning and fail lines with the fix for each - including the palette PNG trap that makes Windows reject a file.
Rebuild a clean, Windows-ready copy with the same pixels: 32-bit bitmaps, an RGBA PNG for 256×256, one layer per size, missing sizes filled in.
CUR files show their hotspot and can be tried live. Animated ANI cursors play with their real timing, frame by frame.
The icon directory with declared vs actual values, bitmap headers, and a colour-coded hex view you can search.
Our own ICO, BMP and PNG decoder runs in your browser. Nothing is uploaded, not even for the checks.
An icon can look perfect in a browser and still be refused by Windows.
Windows (Photos, Explorer, shortcuts) reads ICO files much more strictly than browsers do.
These are the problems the viewer checks for, and what fixes them.
| Problem | What you see | Fix |
|---|---|---|
| Palette (indexed) PNG inside | "Can't open this file" in Photos, a blank icon in Explorer | Store PNG layers as 32-bit RGBA |
| PNG used for small sizes | Missing or broken sizes in older apps and GDI+ | PNG only for 256×256, bitmaps for the rest |
| Wrong bit depth in the directory | Windows picks the wrong layer or a blurry one | Bit count must match the image data |
| Missing sizes | Soft, upscaled icons on the taskbar or desktop | Include 16, 24, 32, 48 and 256 |
| Empty 32-bit alpha | Hard, jagged edges | Real alpha in every 32-bit layer |
| Truncated file | Some sizes missing or the file will not open | Download or export the icon again |
The Download fixed ICO button applies all of these at once. Starting from scratch? PNG to ICO and JPG to ICO already write icons this way, and the Icon Resizer adds missing sizes.
One ICO file can hold many sizes, and Windows and browsers pick the one that fits.
| Size | Used for |
|---|---|
| 16×16 | Browser tabs, bookmarks, Explorer details and small icons, title bars |
| 24×24 | Windows 11 taskbar at 100% scaling |
| 32×32 | Tabs on HiDPI screens, Windows 10 taskbar, Alt+Tab |
| 48×48 | Desktop and medium icons; Google Search likes favicons in multiples of 48 |
| 64 to 128 | Large icons at higher display scaling |
| 256×256 | Explorer large and extra large icons, Windows 10 and 11 tiles |
A website only needs 16, 32 and 48 in its favicon.ico - the Favicon Generator builds that plus the PNG icons for phones. Apps need the full set up to 256. If the file got heavy, Compress ICO slims it down.
An ICO file is a small container for icon images.
A 6-byte header and a directory list each image: its size, colour depth and where its data starts.
Each image is either a bitmap (BMP data with a 1-bit transparency mask) or, since Windows Vista, a PNG. Bitmaps come in 1, 4, 8, 16, 24 and 32-bit flavours - only 32-bit has smooth alpha edges.
A CUR file is the same container with a hotspot instead of the colour info, and an ANI file is a RIFF file that strings cursor frames together with a timing table. To turn icons into other formats, try ICO to PNG, ICO to JPG or ICO to ICNS for Mac.
Viewing other image files? Browse all file viewers, or open Mac icons in the ICNS Viewer.
Drop the .ico file onto this page or click to browse. Every image inside it opens at once - each size as its own card with its bit depth, format and byte size.
Nothing to install, and it works on Windows, Mac, Chromebooks and phones.
The most common cause is a palette (indexed) PNG stored inside the icon - Windows Photos and Explorer then reject the whole file, even though browsers show it fine.
Other causes are a wrong bit depth in the directory, a truncated file or bitmaps without a doubled height. The Checks view names the exact problem, and Download fixed ICO rebuilds a clean copy.
For a Windows app or shortcut: 16, 24, 32, 48 and 256 pixels, all 32-bit. For a website favicon.ico: 16, 32 and 48 is plenty.
Missing sizes can be added with the Icon Resizer.
Yes. Static .cur cursors show their hotspot as a crosshair, and you can try the cursor live in the In use view.
Animated .ani cursors play with their real frame timing, and you can step through or export every frame.
Press PNG on the layer card you want - it downloads with its transparency intact. All layers gives you every size at once (a ZIP when there are more than two).
For batch work, ICO to PNG does the same for many files.
It rebuilds the file the way Windows likes it: 32-bit bitmaps with a transparency mask for the small sizes, a 32-bit RGBA PNG for 256×256, one layer per size and a correct directory.
Existing layers keep their exact pixels, and missing standard sizes are scaled down from a bigger layer (switch that off in Options). The fixed copy also opens in the viewer so you can see the checks turn green.
Windows needs an exact size for each place it shows an icon. When a size is missing it scales another layer - and scaling a small layer up looks soft.
The In use view shows which layer Windows picks at 100% to 200% display scaling.
No. The viewer reads and decodes the file in your browser with its own ICO, BMP and PNG decoder.
Nothing is sent to a server, so it is safe for unreleased app icons and client work.
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