ICO vs JFIF — 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 JFIF

A detailed comparison of ICO Icon and JFIF Image — file size, quality, compatibility, and which format to choose for your workflow.

Convert JFIF → 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.

About ICO files

JFIF

JFIF Image

Raster & Vector Images

JFIF (JPEG File Interchange Format) is a minimal file format for JPEG encoded images.

About JFIF files

Strengths Comparison

ICO Strengths

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.

JFIF Strengths

Universally compatible — every app that reads JPEG reads JFIF.
Tiny wrapper — adds under 20 bytes to a raw JPEG stream.
Royalty-free by design — that was the 1992 goal.
Specifies pixel density, useful for print.

Limitations

ICO Limitations

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.

JFIF Limitations

Minimal metadata — no camera settings, no GPS, no color profile (EXIF handles those).
Redundant with EXIF in modern camera files.
The .jfif extension itself confuses users — almost always safe to rename to .jpg.
Aging — successor roles now split between JPEG XL and AVIF.

Technical Specifications

Specification	ICO	JFIF
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+)	—
Extensions	—	.jfif, .jfi, .jpg, .jpeg
Standard	—	ITU-T T.871 / ISO/IEC 10918-5:2013
Magic bytes	—	FF D8 FF E0 ... 4A 46 49 46 00 ("JFIF\0")
Practical note	—	Safe to rename .jfif → .jpg in virtually all cases

Typical File Sizes

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

JFIF

Web photo (identical to JPEG) 200-500 KB
Camera photo (24 MP) 6-12 MB

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Convert between ICO and JFIF online, free, and without installing anything. Encrypted upload, automatic deletion after 60 minutes.

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Frequently Asked Questions

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.