Resize ICO

How to Resize ICO Files Online

1. Choose Your ICO Files: Drag and drop ICO images onto the page or click "Choose ICO files" — up to 50 at once. The first photo opens in the editor and the rest line up as thumbnails below it; with two or more photos open, "Add more" adds files to the same batch.
2. Set the New Size: In Resize, type a "Width" or "Height" in pixels or percent — with "Keep aspect ratio" on, the other side follows — or pick a "Size preset" (an icon size from 16 to 256 px, percent of original, a target height, or a platform size such as an Instagram post). The size applies to every photo in the batch.
3. Pick the Output Format (Optional): "Save as" keeps "Same as original" or saves as JPG, PNG, WebP or another format. For JPG, WebP and AVIF output, the "Quality" slider (40–100) trades file size against detail. Resize, Crop, Rotate and Flip all work in the same session, and "Undo" steps back.
4. Download: Click the Download button, which names the output format (for example "Download PNG"), for one photo, or "Download all (.zip)" for a batch — "Download one by one" saves the files separately. The editor opens ICO files right in your browser whenever your browser can decode them, so those files are not uploaded. A file it can't decode is either processed on our servers and deleted automatically afterward — the editor says so before you download — or skipped with a note. No sign-up, no watermark.

Why Resize ICO Files?

ICO is the legacy Windows icon container, but it remains the format browsers reach for first when they request /favicon.ico from your site root. One ICO can hold several bitmaps at different sizes and bit depths, and the browser or OS picks the one closest to the display target. Resizing an ICO is rarely about a single dimension — it's about producing the right set of sizes inside one file so a 16x16 browser tab and a 256x256 Windows tile both look sharp.

• Standard favicon set — Most sites ship a single favicon.ico containing 16x16, 32x32, and 48x48 entries. These are the three sizes the W3C favicon convention and Microsoft have documented as the practical baseline for browsers, taskbars, and desktop shortcuts.
• High-DPI displays — Retina, 4K, and Windows scaling at 150-200% pulls the 32x32 or 48x48 entry instead of 16x16. Stripping out the high-res entries to "save bytes" leaves the icon blurry on most modern monitors.
• Windows app icons — Win32 executables embed ICO resources at 16, 24, 32, 48, 64, 128, and 256 pixels. Resizing a master PNG down to each size and packing them into one ICO is the standard build step.
• Replacing a stretched favicon — If your favicon.ico is currently a single 32x32 entry, Chrome and Safari will upscale it to fill the bookmarks bar and tab title on 4K screens. Adding a 48x48 or 64x64 entry fixes the blur without changing the URL.
• Web performance — A favicon.ico with five sizes typically lands under 15 KB. Dropping the rarely-used 96x96 and 128x128 entries when you also serve PNG/SVG favicons via <link rel="icon"> keeps the request small without losing browser compatibility.
• Legacy Windows compatibility — Pre-Vista Windows can't read PNG-compressed entries inside an ICO and tops out at 32-bit color at smaller sizes. If you still ship installers for Windows XP/7, keep your largest entry at 48x48 BMP rather than 256x256 PNG.

Need to start from a different format? Convert PNG to ICO, JPG to ICO, or SVG to ICO first, then resize the resulting ICO here to add the full size set.

Standard Favicon and Icon Sizes — Which to Include

The favicon.ico itself only needs 16, 32, and 48; everything 180 and above belongs in PNG files referenced from your HTML or Web App Manifest.

ICO Bit Depth and Storage — What Goes Inside an ICO

Modern tools default to 32-bit RGBA for every entry. PNG-compressed storage inside ICO has been supported in Windows since Vista (2007) and in every major browser for over a decade — there is no practical reason to ship raw 256x256 BMP entries anymore.

Frequently Asked Questions

Why does my favicon look blurry on a Retina or 4K display?

Browsers pick the entry closest to the requested device-pixel size. If your favicon.ico contains only a 16x16 entry, a Retina MacBook tab (which actually renders the favicon at 32x32 physical pixels) upscales that 16x16 by 2x — producing visible blur. Add at least a 32x32 entry, and ideally 48x48, so the browser has a sharper source for high-DPI scaling.

Should I include a 256x256 entry in my favicon.ico?

Probably not. 256x256 is intended for Windows Explorer "Extra Large Icons" view and Windows app icons, not browser favicons. Including it in your site's /favicon.ico adds 5-30 KB to a file requested on nearly every page load. Modern best practice: ship 16/32/48 in the ICO and serve 180x180 (Apple) and 192x192/512x512 (Android/PWA) as separate PNG files declared in your HTML head and Web App Manifest.

Will upscaling a small ICO to a larger size look good?

No. ICO entries are bitmaps — upscaling a 16x16 entry to 64x64 produces blocky, jagged edges no matter what resampling algorithm the resizer uses. Always work from the largest source you have (ideally a 256x256 or 512x512 PNG, or better, a vector SVG/AI master) and downscale to each target size. If you only have a 16x16 ICO, redraw the icon at a larger size before resizing — the upscale path can't recover detail that was never captured.

Can one ICO file really hold multiple sizes?

Yes — that's the format's defining feature. The ICO header is a directory with one entry per embedded image, and the file can technically contain up to 65,535 entries (the IDCount field is a 16-bit unsigned integer). In practice, favicon.ico files hold 3-6 entries (16/32/48 plus optional 64 and 96) and Windows app ICOs hold 6-9 entries (16/24/32/48/64/128/256). Browsers and the OS automatically pick whichever embedded size is closest to the display target.

Does resizing preserve transparency?

Yes, as long as the source ICO uses 32-bit RGBA (the standard since Windows XP). Each resized entry keeps the alpha channel. If your source is an older 24-bit ICO with a 1-bit AND-mask, edges may show a colored fringe after downscaling — the workaround is to convert the master to 32-bit RGBA first, then resize.

What's the maximum size an ICO can store?

256x256 pixels. The width and height fields in the ICO directory entry are single bytes, with the value 0 used to represent 256 (since 256 itself doesn't fit in 8 bits). For anything above 256x256 — Android 512x512 icons, PWA splash screens, macOS app icons at 1024x1024 — you need PNG or ICNS, not ICO.

Can I add a brand-new size to an existing ICO?

Not directly — you need to rebuild the ICO with the new entry. Open your existing ICO here (the editor opens its largest entry and says so), set the new size with "Width" and "Height" or an "Icon sizes" preset, and download: the saved ICO holds the standard 16, 32 and 48 px entries smaller than your size plus the size you chose (up to 256), and the note names them. Other sizes in the old file are not carried over. For a fresh multi-size ICO built from a single high-resolution source, start with a 256x256 or larger PNG master and convert it via PNG to ICO, which packs the standard 16/32/48 entries automatically.

How small can a favicon.ico get?

A well-built 16+32+48 favicon.ico with 8-bit indexed entries for the 16x16 and 32-bit RGBA for the 48x48 typically lands at 4-6 KB. PNG-compressed 32-bit entries can push it under 4 KB. If you're seeing 30 KB+, the file likely contains unnecessary 128x128 or 256x256 entries, or every size is stored as uncompressed 32-bit BMP — both fixable by resizing here, which rebuilds the file with PNG-compressed entries: pick 48 and the saved ICO holds just 16, 32 and 48.

What if I just need a single-size PNG instead of an ICO?

Use ICO to PNG to extract the largest entry as a PNG (handy for design tools that don't read ICO), or Compress ICO if your goal is shrinking an existing multi-size file. Crop ICO is useful when the source icon has whitespace padding you'd like to trim before downscaling to 16x16.