ICO vs JXL — 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 JXL

Um comparativo detalhado de ICO Icon e JPEG XL Image — tamanho de arquivo, qualidade, compatibilidade e qual escolher de acordo com seu fluxo de trabalho.

Converter JXL → 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 os arquivos ICO

JXL

JPEG XL Image

Raster & Vector Images

JPEG XL is a next-generation image codec designed to replace JPEG with better compression, lossless transcoding from existing JPEGs, and progressive decoding. Browser support is still emerging.

Sobre os arquivos JXL

Comparativo de vantagens

ICO 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.

JXL Vantagens

Lossless JPEG re-encoding — migrate billions of JPEGs without any quality loss.
Best-in-class lossless compression — typically beats PNG by 30-50%.
Single format for web, print, HDR, and archival workflows.
Progressive decoding with fine-grained previews.
Patent-free and royalty-free.

Limitações

ICO 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.

JXL Limitações

Chrome removed support in 2022; desktop ecosystem adoption stalled.
Editor/tool support lags behind AVIF and HEIC.
Encoding is CPU-heavy, particularly for high-quality settings.
Two-camera market (AVIF vs JPEG XL) confuses publishers choosing a modern format.

Especificações técnicas

Especificação	ICO	JXL
MIME type	image/vnd.microsoft.icon	image/jxl
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	—	.jxl
Standard	—	ISO/IEC 18181 (2021)
Max dimensions	—	1 073 741 824 × 1 073 741 824 px (effectively unbounded)
Bit depth	—	Up to 32-bit float per channel

Tamanhos típicos de arquivo

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

JXL

Web photo (1920px, lossy) 100-400 KB
Lossless from JPEG source Original JPEG size × 0.8
Lossless from PNG source Original PNG size × 0.6
HDR photo (12-bit, 4K) 500 KB - 2 MB

Pronto para converter?

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Converter JXL para ICO

Perguntas frequentes

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.