ICO vs JPG — 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 JPG

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

ICO → JPG umwandeln JPG → 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

JPG

JPEG Image

Raster & Vector Images

JPEG is the most widely used lossy image format on the web. It achieves small file sizes through adjustable compression, making it ideal for photographs and complex images where some quality loss is acceptable.

Über JPG-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.

JPG Vorteile

Excellent compression ratio for photographs (10:1 or better without visible quality loss).
Universal support — every camera, phone, OS, and browser reads JPEG natively.
Adjustable quality setting balances file size against visual fidelity.
Embeds EXIF metadata (camera model, GPS, exposure) automatically.
Progressive rendering for graceful loading over 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.

JPG Einschränkungen

Lossy — every save degrades the image further (generation loss).
No transparency channel (use PNG or WebP for that).
Visible compression artifacts on text, sharp edges, and flat colors.
Limited to 8 bits per channel — poor for HDR or print work.
Baseline JPEG tops out at 65,535 × 65,535 pixels.

Technische Spezifikationen

Spezifikation	ICO	JPG
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 — Discrete Cosine Transform + quantization + Huffman coding
Color depth	—	8 bits per channel (24-bit RGB or 8-bit grayscale)
Max dimensions	—	65,535 × 65,535 pixels (baseline)
Transparency	—	Not supported
Typical quality	—	75–90 for web, 95+ for print

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

JPG

Phone photo (12 MP, quality 85) 2–5 MB
Web thumbnail (400px) 20–60 KB
Full-page magazine photo 500 KB – 2 MB
Social-media square (1080×1080) 100–400 KB

Bereit zum Umwandeln?

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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.