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

Q: What is an ICO file?

ICO (Icon) is Microsoft&#039;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 &lt;link&gt; tags in HTML.

ICO vs INDD

Una comparativa detallada de ICO Icon y Adobe InDesign — tamaño de archivo, calidad, compatibilidad y cuál elegir según tu flujo de trabajo.

Convertir INDD → ICO

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.

Sobre los archivos ICO

INDD

Adobe InDesign

Raster & Vector Images

INDD (InDesign Document) is the native file format for Adobe InDesign, the industry-standard desktop publishing application. It stores complex page layouts with typography, images, and interactive elements for magazines, brochures, and books.

Sobre los archivos INDD

Comparativa de ventajas

ICO Ventajas

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.

INDD Ventajas

Native format of the industry-standard page layout app.
Preserves every InDesign feature — styles, master pages, indexes, tables.
Professional prepress metadata (color profiles, overprint, bleed, trap).
Tight integration with Creative Cloud for collaborative editing.

Limitaciones

ICO Limitaciones

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.

INDD Limitaciones

Proprietary — only Adobe InDesign opens INDD natively.
File size grows fast with linked high-res images.
Backward compatibility is version-limited — InDesign 2024 cannot save as InDesign 2020 without IDML export.
Subscription-locked since 2013.

Especificaciones técnicas

Especificación	ICO	INDD
MIME type	image/vnd.microsoft.icon	application/x-indesign
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+)	—
Extension	—	.indd, .indl (library), .inds (snippet), .indt (template)
Container	—	Proprietary binary
Interchange	—	IDML (ZIP + XML)
Native app	—	Adobe InDesign

Tamaños típicos de archivo

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

INDD

Simple 4-page brochure 1-5 MB
32-page magazine with linked photos 10-50 MB
300-page illustrated book 100-400 MB

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Preguntas frecuentes

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.