Can I view the icons inside Windows system DLLs?

Yes. Open a system DLL such as shell32.dll or imageres.dll and the viewer previews every icon inside it. One catch on Windows 11 and Windows 10 1903 or later: the icon data was moved into matching .mun files in C:\Windows\SystemResources, so open shell32.dll.mun rather than shell32.dll or the file will look empty.

How do I check my favicon.ico contains the right sizes?

Open it in an ICO viewer. A favicon should carry at least 16x16 for the browser tab, 32x32 for bookmarks and taskbar shortcuts, and 48x48 for pinned tiles. If only one size comes back, browsers are scaling that single image everywhere, which is what makes a favicon look soft in the tab.

Univik ICO File Viewer

ICO Viewer: Open ICO Files and Preview Every Icon Size

Free ICO File Viewer for Windows 11, 10, 8 and 7

Open any .ico file and see every icon size it contains, from 16x16 up to 512x512. The same tool reads icon resources embedded inside .dll libraries and .exe applications, so you can pull out icons Windows never exposes on its own. Preview it online in your browser with no upload, or install the free Windows app for DLL and EXE files.

View all icon sizes from ICO files (16x16 to 512x512)
Preview every icon inside DLL files at all resolutions
Preview every icon inside EXE files instantly
Save any previewed icon as PNG or ICO

100% Free No Registration Windows 11 Ready VirusTotal Verified

Free Download
Windows app, 8.5 MB

Open ICO Online

*Completely free for personal and commercial use. No registration required.

Univik ICO File Viewer for Windows

100% Free Software

No trial, no limitations, no registration. Free for personal and commercial use.

Online ICO Viewer

Open ICO Files Online in Your Browser

Drop an .ico file below to preview every icon size stored inside it. Your file is read by your own browser and is never uploaded to any server. To open icons inside .dll and .exe files, or to process a whole folder at once, use the free Windows app.

Choose an ICO file or drag it here Nothing is uploaded. All processing happens on your device.

Supports every standard ICO layout: PNG compressed entries and 32, 24, 8, 4 and 1 bit BMP entries, including alpha transparency and AND mask transparency.

How the Viewer Reads Your ICO File

An ICO is not one picture. It is a small index followed by the images it points at, and the viewer walks that index byte by byte rather than handing the file to the browser and hoping for the best. That is why it can show you every size instead of one.

Position	What it holds
Bytes 0 to 1	Reserved, always `00 00`
Bytes 2 to 3	Type. `01 00` marks an icon, `02 00` marks a cursor
Bytes 4 to 5	How many images the file contains
Then, 16 bytes each	One ICONDIRENTRY per image: width, height, colour count, colour planes, bits per pixel, byte size and the offset where that image starts
After the index	The image data itself, one block per entry

Three details that trip up simpler viewers:

A width or height of zero means 256. The field is a single byte, and 256 does not fit in one byte, so the format writes 00 and expects the reader to know. A viewer that takes the byte literally reports a 0x0 icon.
Each image is stored one of two ways. Since Windows Vista an entry can hold compressed PNG data, recognised by the 89 50 4E 47 signature at its start. Otherwise it is an uncompressed BMP bitmap, stored as a DIB with no file header.
DIB entries declare double their real height. The extra half is a 1-bit AND mask sitting underneath the colour data, which is how icons handled transparency before alpha channels. At 32-bit an icon carries a proper 8-bit alpha channel instead. At 1, 4, 8 and 24-bit the AND mask is the only transparency there is, and a reader that ignores it renders a black or white box behind your icon.

The picker accepts anything the system reports as image/vnd.microsoft.icon or image/x-icon. Cursor files (.cur) open too, since they use the same layout with two hotspot coordinates added to each entry. Animated cursors (.ani), macOS icon files (.icns) and Windows icon libraries (.icl) use different containers and will not open here.

Which ICO Viewer Should You Use?

Most online ICO viewers upload your file to a server. These do not.

Capability	Upload based online viewers	Univik browser viewer	Univik Windows app
File sent to a server	Yes	No	No
Opens .ico files	Yes	Yes	Yes
Shows every embedded size	Sometimes	Yes	Yes
Opens .dll and .exe files	No	No	Yes
Daily upload limits	Common	None	None
Works offline	No	After first load	Yes
Cost	Free with limits	Free	Free

Viewable Icon Properties

What the ICO Reader Shows for Every Icon

Icon Image

Visual Preview

Dimensions

Width × Height

Color Depth

Bits Per Pixel

Transparency

Alpha Channel

File Size

Bytes / KB

Icon Index

Resource Position

Format Type

BMP / PNG

Resource ID

DLL/EXE ID

Supported File Types

Windows Icon Viewer for ICO, DLL and EXE Files

Preview icons from every standard Windows icon container, not just standalone icon files.

ICO

ICO Files

View all icon sizes embedded in .ico files. Windows icon files can contain multiple resolutions from 16x16 to 512x512 pixels, and our viewer displays them all.

16x16 32x32 48x48 256x256

DLL

DLL Files

See every icon inside a Dynamic Link Library. DLL files hold icon resources that Windows never exposes as files, and the viewer displays all of them.

shell32.dll imageres.dll Custom DLLs

EXE

EXE Files

See the icons inside an executable. View the main application icon and any additional icon resources embedded in a .exe file.

App Icons Toolbar Icons Resource Icons

All Resolutions Supported

View Every Icon Size from 16x16 to 512x512

A single ICO file can hold eight or more separate images. Windows picks one and hides the rest. This viewer shows all of them.

16×16

24×24

32×32

48×48

64×64

128

128×128

256

256×256

512

512×512

Why One Icon Needs So Many Sizes

Windows does not scale a single image up and down. It reaches into the ICO and picks the version built for the spot it is filling. Shipping an icon with a size missing means Windows stretches the nearest one it can find, and that is where blurry taskbar icons come from. This is exactly what you cannot check by opening the file in Photos, because Photos only ever shows you one of them.

Where the icon appears	Size Windows reaches for
Taskbar and the system tray	16×16 and 24×24
File Explorer in list or details view	16×16
Alt+Tab switcher and the Change Icon dialog	32×32
Desktop shortcuts and Explorer medium icons	48×48
Start menu and search results	32×32 to 48×48
Explorer large icons	96×96
Explorer extra large icons and previews	256×256

On a high DPI display every one of those doubles. At 200% scaling a taskbar asking for 16×16 is really asking for 32×32, which is why a modern icon carries sizes an older one never needed. Icons built before Windows Vista often stop at 48×48, and on a 4K screen it shows.

The same logic applies on the web. A favicon.ico usually bundles 16×16, 32×32 and 48×48 so a browser tab, a bookmark and a pinned shortcut each get a purpose-built version. Drop yours into the viewer above to confirm all three are actually in there. For how the format packs them, see our guide to what an ICO file is.

Key Features

ICO File Viewer Features

Everything you need to open, inspect and compare icons from Windows icon containers.

Multi-Size Preview

View all available icon sizes side by side. Instantly see how your icons look at every resolution from 16x16 to 512x512 pixels.

See Inside DLL and EXE

Open a DLL or EXE and every embedded icon resource is detected and displayed automatically, with no resource editor needed.

Save as PNG or ICO

Save any icon you are previewing as a PNG with transparency or as an ICO. One size, or every size at once.

Nothing Leaves Your PC

The desktop app makes no network connections and the browser viewer never uploads. Icons from private DLL and EXE files stay private.

Icon Search

Narrow a long icon list down to the one you are after. Useful when a single system library holds several hundred of them.

Alpha Channel Preview

See exactly where an icon is transparent. Every preview sits on a checkerboard so soft alpha edges are visible rather than guessed.

Beyond ICO Files

See the Icons Hidden Inside DLL and EXE Files

Most Windows icons never exist as standalone .ico files. They are compiled into DLL libraries and EXE executables as resources, which is why an ordinary image viewer has no way to reach them. Open the file in Univik ICO File Viewer and every icon resource inside it is listed and previewed, at every size, with no resource editor required.

What the viewer is for

Seeing what icons a file actually contains
Checking sizes, colour depth and resource index
Grabbing one icon you need as PNG or ICO

When you need more than viewing

Pulling every icon out of many files at once
Converting EXE to ICO, or ICO to PNG in bulk
BMP output and folder level processing

That is the Univik ICO Converter.

If a Windows system DLL looks empty, check the .mun file

Since Windows 10 version 1903, Microsoft moved the icon resources out of the System32 DLLs into matching compressed .mun files in C:\Windows\SystemResources. Open shell32.dll.mun instead of shell32.dll and the icons appear normally. This is the single most common reason a working method looks broken. Our guide to extracting icons from EXE and DLL files on Windows 11 and 10 covers the .mun change and the free extraction methods in full.

Can I put an ICO file back into a DLL?

No. Univik ICO File Viewer reads icons out of DLL and EXE files, it does not write them back in. Building or editing a DLL icon library needs a resource editor such as Resource Hacker. If what you actually need is the icons themselves as separate files, open the file here and save the ones you want.

Use Cases

Who Uses ICO File Viewer?

Built for professionals who work with Windows icons and application resources.

Inspecting App Icons

Developers checking what icon resources an application ships, and at which sizes, before referencing them in a project.

Checking Sizes and Sharpness

Designers confirming an icon still reads clearly at 16x16, not just at 256x256, across every size in the file.

Auditing System Icons

Administrators looking inside a system library to identify the exact icon and index needed for documentation or tooling.

Grabbing a Single Icon

Writers and creators who need one high resolution icon for a tutorial, blog post or Windows explainer.

Step by Step

How to Open an ICO File on Windows 11 and Windows 10

Windows has no built in ICO file opener that shows every size an icon contains. These four methods do, starting with the one that needs no installation at all.

Method 1: Open an ICO File in Your Browser

Use the ICO viewer at the top of this page. Select your .ico file and every embedded size appears at once, with its dimensions, colour depth and internal format. Nothing is uploaded, so the file stays on your machine. This works on Windows, macOS, Linux, Android and iOS, and it is the fastest way to preview a single icon file.

Method 2: Open ICO, DLL and EXE Files with Univik ICO File Viewer

The desktop app goes further than any browser can. It reads icon resources out of DLL and EXE files, processes whole folders at once and exports in bulk.

Install and launch. Download the free installer and open Univik ICO File Viewer.
Open your file. Use File then Open, or drag your .ico, .dll or .exe file onto the window.
Browse every icon. All sizes and all embedded resources appear in the thumbnail grid, with dimensions, bit depth and resource index for each.
Save what you need. Select the icon you want and save it as PNG with transparency or as ICO.

Univik ICO File Viewer showing all icon sizes from a Windows ICO file

Method 3: Open an ICO File with Windows Photos or Paint

Right click the .ico file, choose Open with, then Choose another app, and pick Photos or Paint. Both will display the icon, with one important limit: they render only a single image from the file, usually the largest. An ICO file is a container that can hold eight or more separate images at different sizes and colour depths, and Photos gives you no way to see the rest. Use Method 1 or Method 2 when you need to check every size.

What Each ICO Opener Actually Shows You

Plenty of programs will open a .ico file. Almost none of them show you what is inside it. Here is what you actually get from each:

Opener	Shows every embedded size	Shows bit depth and format	Install
Windows Photos	No, one image only	No	Built in
Microsoft Paint	No, one image only	No	Built in
File Explorer thumbnail	No, one per view mode	No	Built in
Chrome, Edge, Firefox, Safari	No, one image only	No	Built in
GIMP	Yes, each size imports as a layer	Partly	Yes
IrfanView	With its extract icons option	No	Yes
XnView	Varies by version	No	Yes
Paint.NET	Needs a third party plugin	No	Yes
Univik ICO Viewer, browser	Yes	Yes	None
Univik ICO Viewer, Windows app	Yes	Yes	Free

GIMP is the useful free alternative if you already have it, because it imports each embedded size as its own layer rather than flattening to one. Paint and Photos will always show a single image, which is why an icon can look fine there and still be broken at 16×16.

Method 4: Set a Default ICO File Opener in Windows 11

To stop choosing an app every time, right click any .ico file, select Open with then Choose another app, pick your viewer, and tick Always use this app to open .ico files. On Windows 11 you can also set it from Settings, Apps, Default apps, then search for the .ico file type. The association then applies to every .ico file on the system.

Not sure what is inside an ICO file in the first place? Read our guide to what an ICO file is and how the format works.

Frequently Asked Questions

ICO Viewer FAQs

There are three ways. Use the browser based ICO viewer on this page, which reads the file locally and shows every embedded size with no upload. Install the free Univik ICO File Viewer for Windows, which also opens DLL and EXE files. Or right click the file, choose Open with and select Photos or Paint, which shows only one image from the file.

Yes. The ICO viewer at the top of this page runs entirely in your browser and shows every icon size inside an .ico file. Unlike upload based online viewers, your file is never sent to a server. The desktop app is only needed for .dll and .exe files.

Yes. Univik ICO File Viewer runs on Windows 11, 10, 8.1, 8 and 7, and opens .ico files plus icons inside .dll and .exe files on all of them. The browser viewer on this page works on any operating system with a modern browser.

ICO File Viewer can open .ico icon files, .dll dynamic link library files and .exe executable files, displaying every icon embedded inside them.

Yes. Whatever the file holds is what you see, from 16×16 up to 512×512, each one listed with its own dimensions and colour depth. Windows only ever shows you one size. The viewer shows you all of them at once.

Yes. Open the .exe in Univik ICO File Viewer and it reads the executable resource table, previewing every embedded icon at every size so you can inspect what is in there. A browser cannot do this, because it has no way to read a Windows resource table. If you need those icons pulled out in bulk and converted, that is a job for the Univik ICO Converter.

Yes. Open a system DLL such as shell32.dll or imageres.dll and the viewer previews every icon inside it. One catch on Windows 11 and Windows 10 1903 or later: Microsoft moved the icon data into matching .mun files in C:\Windows\SystemResources, so open shell32.dll.mun rather than shell32.dll or the file will look empty. Our guide to extracting icons from EXE and DLL files covers this in full.

No. Univik ICO File Viewer reads icons out of DLL files, it does not write them back in. Creating a DLL icon library requires a resource editor such as Resource Hacker. If you need the icons as individual files instead, open the DLL here and export each one as PNG or ICO.

Yes. It handles every common Windows icon source: standalone .ico files, icon resources inside .dll libraries such as imageres.dll and shell32.dll, and icons embedded in .exe applications. For each one it shows the image, dimensions, colour depth, transparency, internal format and resource index.

Every ICO preview lists the icon image plus its width and height, colour depth in bits per pixel, whether it carries an alpha transparency channel, the internal storage format of PNG or BMP, the size in bytes and its index position within the file or resource table.

You can save a previewed icon as PNG with transparency or as ICO, one size at a time or all sizes at once. For BMP output and bulk conversion across many files, use the Univik ICO Converter.

Yes. ICO File Viewer is 100% free to download and use with no hidden costs, watermarks or limitations. No registration required.

Because an ICO is a container, not a picture. It holds an index followed by several complete images at different sizes and colour depths, and Photos renders whichever single one it picks, usually the largest. Paint, File Explorer thumbnails and web browsers all behave the same way. To see every image the file actually contains, use the viewer on this page.

Yes. A .cur file uses the same layout as an ICO with two differences: the type field reads 02 00 instead of 01 00, and each entry carries hotspot coordinates marking the exact pixel the cursor points with. The viewer reads both. Animated cursors (.ani) use a different container and will not open.

Usually one of three things. The commonest is a renamed PNG or JPG: changing the extension to .ico does not convert anything, and the file still has no icon index. Second, the file is truncated or corrupt, so the offsets in the index point past the end of the data. Third, it is an OS/2 icon or an .icl icon library rather than a Windows ICO. A Windows ICO always begins with the four bytes 00 00 01 00. The viewer checks that signature first, so it tells you when a file is not an icon rather than failing silently.

Drop it into the viewer above. A favicon should carry at least 16×16 for the browser tab, 32×32 for bookmarks and taskbar shortcuts, and 48×48 for pinned tiles. If only one size comes back, browsers are scaling that single image everywhere, which is what makes a favicon look soft in the tab.

Technical Data Sheet

ICO File Viewer Technical Specifications

Complete product specifications, system requirements and compatibility information.

Last updated: 27 July 2026

Security Verification

The download location is scanned by VirusTotal. Open the report and check it yourself rather than taking our word for it.

View VirusTotal Report

Supported Input Files

ICO (Windows Icon) - All versions

DLL (Dynamic Link Library)

EXE (Executable Files)

Open one file at a time. For folder and bulk processing, see the ICO Converter.

Product Name:	Univik ICO File Viewer
Version:	25.1
File Size:	8.5 MB
License:	100% Free
Download:	Free Download

Version 25.1

What's New

Improved DLL icon reading
Better PNG export quality
Enhanced thumbnail view
Faster file loading
Multi-language support

Requirements

Hard Disk:	20 MB free
RAM:	512 MB minimum
Processor:	Any modern CPU

Platforms

Windows: 11, 10, 8.1, 8, 7 (32 & 64-bit)

Server: 2022, 2019, 2016, 2012

Save Formats

PNG - With transparency

ICO - Windows icon format

BMP and bulk output: ICO Converter

User Reviews

Reviews and Ratings

Univik ICO File Viewer is published on the Microsoft Store, where every rating comes from a verified install. Read what users say and leave your own review there.

View on Microsoft Store

Need to Convert Icons?

Viewing is one thing, pulling icons out is another. To extract icons from DLL and EXE files in bulk, convert EXE to ICO or export to BMP, use the Univik ICO Converter. For the free manual methods with Resource Hacker, 7-Zip and PowerShell, read our icon extraction guide.

Open ICO Converter

New to icons? Learn what an ICO file is. Browse all our free file viewers.

Multi-Language Support

Available in 10+ Languages

Use ICO File Viewer in your preferred language. The interface is fully translated for global accessibility.

English Español Français Deutsch Italiano Português Русский 中文日本語 한국어

Select your language from the dropdown menu in the application toolbar. Changes apply instantly without restart.

Supported Sources

Open Icons from Any Windows Source

Univik ICO File Viewer opens icons stored in ICO files and embedded in Windows system files, with no development tools required. To learn how the format works inside, see our guide on what an ICO file is.

Common sources of ICO files and icon resources include:

Windows application icons
System DLL files (shell32.dll, imageres.dll)
Executable files (.exe)
Icon libraries and packs
Web favicons

Desktop shortcuts
Toolbar and menu icons
Control panel items
File type associations
Custom application resources

Univik ICO File Viewer lets you open and view icons from any of these sources without specialized development tools. Open the file and browse every available icon size.