Sobre os arquivos ICO
Ícone ICO
Container de ícones do Windows (1985). Empacota múltiplas resoluções (16×16, 32×32, 256×256) em arquivo único — favicon padrão.
Família
Raster & Vector Images
Extensão
.ico
Tipo MIME
image/x-icon, image/vnd.microsoft.icon
Pode ser usado como
COMO NASCEU O
FORMATO ICO.
The ICO file was born on November 20, 1985, the day Microsoft shipped Windows 1.0. Every application icon, every folder glyph, every cursor needed a container, and Microsoft designed .ico as a raw-pixel, multi-resolution bundle: one file holds multiple sizes (16×16, 32×32, 48×48, 256×256) and the OS picks the best one for the current context.
For 15 years ICO was a Windows-only curiosity. Then in 1999 Microsoft quietly slipped a line into Internet Explorer 5: if a site hosts /favicon.ico, the browser will display it in the tab and bookmarks. Overnight every webmaster on Earth needed one. That single convention turned .ico into the most widely requested image file type on the internet — every browser, every day, checks every domain for it.
CURIOSIDADES E
FATOS INTERESSANTES.
Every web browser still requests /favicon.ico on every domain, even in 2026 — it is the most-requested image format on the internet by frequency.
A single .ico file can hold up to 65 535 images of different sizes and color depths, chosen by the OS at display time.
Windows XP introduced 32-bit ICOs with alpha transparency — before that, icons used a magenta-keying trick for transparent areas.
macOS had its own .icns format but Safari still looks for favicon.ico first when fetching a site icon.
The Windows "Blue Screen of Death" sad-face emoji (Windows 10+) is literally an .ico file shipped in the kernel.
VANTAGENS E
LIMITAÇÕES.
Vantagens
- 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.
Limitações
- 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.
Tamanhos típicos de arquivo
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
Especificações técnicas
- MIME type
- image/vnd.microsoft.icon
- 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+)
CONVERTER A PARTIR DE
ICO
CONVERTER PARA
ICO
Casos de uso comuns
Website favicons, Windows desktop icons, application icons.
Formatos relacionados
Comparativos populares
ICO vs PNG
Diferenças, tamanho de arquivo e quando escolher cada formato.
ICO vs JPG
Diferenças, tamanho de arquivo e quando escolher cada formato.
ICO vs WEBP
Diferenças, tamanho de arquivo e quando escolher cada formato.
ICO vs AVIF
Diferenças, tamanho de arquivo e quando escolher cada formato.
ICO vs GIF
Diferenças, tamanho de arquivo e quando escolher cada formato.
ICO vs BMP
Diferenças, tamanho de arquivo e quando escolher cada formato.
Conversões populares de ICO
Os destinos mais procurados ao converter arquivos ICO.
Perguntas frequentes sobre ICO
Perguntas frequentes
ICO (Icon) is Microsoft's 1985 multi-resolution icon formato, originally shipped com Windows 1.0. A single .ico arquivo holds multiple sizes (16×16, 32×32, 48×48, 256×256) so the OS can pick the best one para the current display context. Since 1999, every website uses a favicon.ico to show its icon in browser tabs.
On Windows, ICO arquivos abrir natively in arquivo Explorer e Photos. On macOS, Preview handles basic display. para editing, usar GIMP (free), Photoshop com a plugin, ou dedicated icon editors like IcoFX.
Use the PNG-to-ICO converter on KaijuConverter — enviar a PNG (ideally square, at least 256×256) e baixar a multi-resolution ICO com all padrão favicon sizes embedded.
A complete favicon pack inclui 16×16, 32×32, 48×48, e 256×256 px variants all in one ICO file. The total tamanho do arquivo is tipicamente 5-15 KB. Browsers automatically pick the right size para tabs, bookmarks, e desktop shortcuts.
ICO para /favicon.ico (every browser requests this URL automatically). PNG para everywhere else — social media profile images, in-page icons, app logos. moderno favicon best practice inclui both an .ico at the root e multiple .png sizes referenced via <link> tags in HTML.
Yes. Every browser still requests /favicon.ico on every domain as its first icon fallback. moderno sites tipicamente provide both favicon.ico e altaer-quality SVG ou PNG icons via <link rel="icon"> tags — browsers pick the best match.