ICO vs JPEG — Differences, File Size & When to Use Each

Q: What is an ICO file?

ICO (Icon) is Microsoft's 1985 multi-resolution icon format, originally shipped with Windows 1.0. A single .ico file holds multiple sizes (16×16, 32×32, 48×48, 256×256) so the OS can pick the best one for the current display context. Since 1999, every website uses a favicon.ico to show its icon in browser tabs.

Q: How do I open an ICO file?

On Windows, ICO files open natively in File Explorer and Photos. On macOS, Preview handles basic display. For editing, use GIMP (free), Photoshop with a plugin, or dedicated icon editors like IcoFX.

Q: How do I convert PNG to ICO?

Use the PNG-to-ICO converter on KaijuConverter — upload a PNG (ideally square, at least 256×256) and download a multi-resolution ICO with all standard favicon sizes embedded.

Q: What size should a favicon.ico be?

A complete favicon pack includes 16×16, 32×32, 48×48, and 256×256 px variants all in one ICO file. The total file size is typically 5-15 KB. Browsers automatically pick the right size for tabs, bookmarks, and desktop shortcuts.

Q: ICO vs PNG for web icons: which?

ICO for /favicon.ico (every browser requests this URL automatically). PNG for everywhere else — social media profile images, in-page icons, app logos. Modern favicon best practice includes both an .ico at the root and multiple .png sizes referenced via tags in HTML.

ICO vs JPEG

Ein detaillierter Vergleich von ICO Icon und JPEG Image — Dateigröße, Qualität, Kompatibilität und welches je nach Workflow zu wählen ist.

JPEG → ICO umwandeln

ICO

ICO Icon

Raster & Vector Images

ICO is the icon file format used for favicons and Windows application icons. A single ICO file can contain multiple image sizes and color depths for different display contexts.

Über ICO-Dateien

JPEG

JPEG Image

Raster & Vector Images

JPEG alternate extension. Functionally identical to JPG but uses the four-letter extension. Some older systems and cameras produce files with this extension.

Über JPEG-Dateien

Vorteilsvergleich

ICO Vorteile

Multi-resolution: one file, many sizes, OS picks the right one.
Universal favicon support in every browser since IE5.
Supports transparency (1-bit since 1985, full alpha since XP).
Tiny file size — an entire favicon pack typically fits in under 15 KB.
No licensing or patent concerns — fully in the public domain spec-wise.

JPEG Vorteile

Universally supported — every camera, browser, OS, and editor reads JPEG.
Mature, deterministic, and fast to encode/decode.
Small file sizes for photographs — DCT compression shines on continuous-tone imagery.
Rich metadata ecosystem (EXIF for shooting data, XMP for editing, IPTC for captions).
Progressive variant enables perceived faster loading on slow networks.

Einschränkungen

ICO Einschränkungen

Cannot compress continuous-tone images efficiently — use PNG or WebP for photos.
Format is essentially frozen in 1999 — no HDR, no wide gamut, no modern features.
Maximum image dimension is 256×256 px (inside an ICO container).
Editing requires specialized tools — most image editors treat it as a curiosity.

JPEG Einschränkungen

Lossy by design — every save further degrades quality ("generation loss").
No transparency channel. Logos and UI elements belong in PNG or WebP.
Terrible on flat colors, text, and sharp edges — blocking artifacts are visible.
Limited to 8-bit color — HDR and wide gamut need JPEG XL or AVIF.
Twice the size of WebP and 30-50% bigger than AVIF at comparable quality.

Technische Spezifikationen

Spezifikation	ICO	JPEG
MIME type	image/vnd.microsoft.icon	image/jpeg
Max resolutions per file	65 535 images	—
Max single image size	256×256 px	—
Color depths	1, 4, 8, 24, 32 bits per pixel	—
Compression	Uncompressed bitmap or embedded PNG (Vista+)	Lossy DCT (baseline); lossless mode exists but rarely used
File extensions	—	.jpg, .jpeg, .jpe, .jfif
Standard	—	ITU-T T.81 / ISO/IEC 10918-1:1994
Color depth	—	8-bit per channel (24-bit RGB total)
Max dimensions	—	65 535 × 65 535 px

Typische Dateigrößen

ICO

Classic favicon (16×16 only) < 2 KB
Multi-size favicon pack (16/32/48/256) 5-15 KB
Full Windows app icon set 20-100 KB

JPEG

Thumbnail (400px) 20-60 KB
Web photo (1920px) 200-500 KB
Print-quality photo (3000px) 1-4 MB
DSLR JPEG (24 MP, quality 95) 6-12 MB

Bereit zum Umwandeln?

Wandle zwischen ICO und JPEG online um, kostenlos und ohne Installation. Verschlüsselter Upload, automatische Löschung in 60 Minuten.

JPEG zu ICO umwandeln

Häufig gestellte Fragen

ICO (Icon) is Microsoft's 1985 multi-resolution icon format, originally shipped with Windows 1.0. A single .ico file holds multiple sizes (16×16, 32×32, 48×48, 256×256) so the OS can pick the best one for the current display context. Since 1999, every website uses a favicon.ico to show its icon in browser tabs.

On Windows, ICO files open natively in File Explorer and Photos. On macOS, Preview handles basic display. For editing, use GIMP (free), Photoshop with a plugin, or dedicated icon editors like IcoFX.

Use the PNG-to-ICO converter on KaijuConverter — upload a PNG (ideally square, at least 256×256) and download a multi-resolution ICO with all standard favicon sizes embedded.

A complete favicon pack includes 16×16, 32×32, 48×48, and 256×256 px variants all in one ICO file. The total file size is typically 5-15 KB. Browsers automatically pick the right size for tabs, bookmarks, and desktop shortcuts.

ICO for /favicon.ico (every browser requests this URL automatically). PNG for everywhere else — social media profile images, in-page icons, app logos. Modern favicon best practice includes both an .ico at the root and multiple .png sizes referenced via <link> tags in HTML.

Yes. Every browser still requests /favicon.ico on every domain as its first icon fallback. Modern sites typically provide both favicon.ico and higher-quality SVG or PNG icons via <link rel="icon"> tags — browsers pick the best match.