ICO to AVIF Converter
Convert ICO to AVIF in your browser. ICO files usually come from website favicons, Windows programs and installers; AVIF is the better fit for maximum compression on modern websites. You get an AVIF encoded with libavif (AV1) compiled to WebAssembly, at the quality you choose. Nothing is uploaded.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
ICO expected · other image formats also work
How to use ICO to AVIF
- 1
Add your ICO files: drop them here, choose them, or paste from the clipboard.
- 2
Set the quality. AVIF quality numbers run lower than JPEG: around 55 to 65 already looks excellent. Encoding is slow on phones.
- 3
Click Convert. Each file is decoded and encoded in a background thread on this device.
- 4
Download the .avif files one at a time or together as a ZIP.
Why use Aback Images for ico to avif
Where the AVIF goes next
AVIF opens in Chrome, Edge, Firefox, Safari 16 and later, Windows 11 Photos, macOS Preview and recent editors.
AVIF next to ICO
A lossy AVIF usually comes out far smaller than the ICO, which stores each size stored as a headerless BMP or as a complete PNG.
The first lossy pass
The ICO holds 1 to 32 bits per pixel, set per size with nothing discarded yet. This conversion is the first lossy encode these pixels see, and hard edges and flat colour show it first.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
ICO vs AVIF
What changes from ICO to AVIF
Encoding: the ICO uses each size stored as a headerless BMP or as a complete PNG; AVIF uses lossy or lossless AV1 intra-frame coding, and the download is an AVIF encoded with libavif (AV1) compiled to WebAssembly, at the quality you choose.
Bit depth: 1 to 32 bits per pixel, set per size in the ICO; AVIF allows 8, 10 or 12 bits per channel, and the AVIF written here has 8 bits per channel.
Colour: RGB or a palette, per image in the ICO; AVIF supports YUV 4:4:4 or 4:2:0 with BT.709, Display P3 or BT.2020 primaries, HDR curves possible, written here as 8-bit sRGB.
Transparency: the ICO stores it as 8-bit alpha in 32-bit and PNG entries, or a 1-bit mask in old icons; the AVIF keeps it as an auxiliary AV1 image stored beside the colour image.
Other images: the ICO can hold several sizes of the same picture, typically 16, 32, 48 and 256 px; only the main image is converted.
Metadata: the ICO can carry only a directory of the sizes inside, with no EXIF; AVIF can carry EXIF, XMP and ICC stored as HEIF items, but nothing is copied across.
About ICO
ICO is a container that bundles several sizes of the same icon (16, 32, 48, 256 px) into one file. It is still the most compatible format for website favicons and Windows app icons.
An ICO starts with a 6-byte ICONDIR (type 1 for icons) and a 16-byte entry per image giving width, height, colour count and offset. Each image is either a BMP without its file header plus an AND mask, or a complete PNG.
ICO files usually come from website favicons, Windows programs and installers.
About AVIF
AVIF uses the AV1 video codec for still images. It is the most efficient widely supported format, often half the size of JPEG, with HDR, wide colour and transparency, but encoding is slow.
An AVIF is a HEIF file, the same ISO base media boxes as MP4, with the brand 'avif'. The picture is an AV1 key frame stored as an image item, and its size, colour and pixel layout are item properties.
When converting ICO to AVIF makes sense
AVIF is the better choice for maximum compression on modern websites, while ICO suits favicons and Windows icons.
AVIF strengths: Often 50% smaller than JPEG; Excellent at low quality settings; Transparency, HDR and 10/12-bit colour. Drawbacks to weigh: Slow to encode, especially on phones; Not supported by some older software; Can smooth away fine texture at low quality.
Limitations
- The largest image in the icon is the one converted; smaller sizes that were hand-tuned for 16 px are not carried over.
- Icons are small and hard-edged, so lossy encoders show ringing around the outline quickly.
- AVIF encoding is CPU-heavy, so large images and big batches take noticeably longer than JPG or WebP, especially on phones.
- Some older apps and operating systems cannot open AVIF yet; keep a JPG copy if you share the file widely.
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Frequently asked questions
Does converting ICO to AVIF lose quality?
AVIF is lossy, so detail the eye barely notices is discarded to save space. Not carried over: any several sizes of the same picture.
Is transparency kept in the AVIF?
Yes. ICO stores it as 8-bit alpha in 32-bit and PNG entries, or a 1-bit mask in old icons, and the AVIF is written with an alpha channel, so transparent areas stay transparent.
What quality should I choose for AVIF?
AVIF quality numbers run lower than JPEG: around 55 to 65 already looks excellent. Lower values give much smaller files with gentle softening. Encoding is CPU-heavy, so large batches take a while on phones.
Which apps open AVIF files?
Chrome, Edge, Firefox, Safari 16 and later, Windows 11 Photos, macOS Preview and recent editors. It opens in Chrome 85+, Edge, Firefox 93+ and Safari 16+.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.