Convert ICO to GIF
An ICO is not one image. It is a container holding the same artwork at several sizes so Windows can pick the right one for a taskbar, a title bar or a desktop. Converting to GIF means choosing, and this route takes the largest stored size because that is the one with detail to lose. GIF's transparency is one bit, so a soft icon edge becomes a hard one.
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What it does
- The largest size inside the container is used
- Palette built from the colors present, capped at 256
- One-bit transparency: a pixel is clear or it is not
How to use ICO to GIF
- 1
Upload the .ico
A favicon or an application icon. It may hold 16, 32, 48 and 256 pixel versions; you do not need to know which.
- 2
The biggest frame wins
The container is read and the largest stored image is taken. Starting from the largest means a later resize still has pixels to work with.
- 3
Look at the edge
Icons are usually drawn with anti-aliased edges over transparency. GIF cannot hold a half-transparent pixel, so that soft edge is resolved to a hard one.
How it works
The container's directory is read first: it lists every image inside, with its width, height and color depth. The largest entry is selected and decoded to a plain raster. That raster is then reduced to a palette of at most 256 colors and written as a GIF.
Reading the directory rather than guessing matters, because ICO files vary wildly. A favicon from 2008 may hold nothing but a 16 pixel image; one exported by a modern design tool commonly holds a 256 pixel entry alongside the small ones.
What the format change costs
Two things are given up. The first is color depth beyond 256 entries, which for icon artwork is usually free, because most icons are drawn with a limited palette anyway.
The second is the alpha channel, and that one is rarely free. Icons are drawn to sit on unknown backgrounds, so their edges are anti-aliased into transparency. GIF has only a single transparent color, so each of those partly-transparent pixels must be resolved. On a busy background the join will show.
When to use something else
If the icon is going onto a web page or into a document with a colored background, PNG is the better target: it keeps the soft edge and the full color range. GIF is the right answer when the receiving system is old, refuses PNG outright, or when the artwork is flat enough that one-bit transparency costs nothing.
What is preserved
The pixel dimensions of the chosen frame, the drawing itself, and any color that fits inside the palette. Nothing is resized and nothing is sharpened.
An icon file holds several sizes
ICO is a container rather than a single image. A well-made one holds the same icon at 16, 32, 48 and often 256 pixels, so that Windows can pick the right one for a menu, a desktop or a preview pane.
A GIF holds one image, so the largest is taken — upscaling a 16-pixel version would be a visible mistake, while downscaling the largest is what you would have done by hand.
Transparency survives, because both formats support it, though GIF's is a single fully-transparent color rather than ICO's smooth alpha. On an icon with soft edges that shows as a hard, slightly ragged outline.
Examples
A favicon for a documentation page
The 48 pixel version is taken rather than the 16, so the GIF is the most detailed frame the file contained. Anything smaller can be produced from it later.
A 256-pixel application icon
The result is smaller and the shape is intact, but the anti-aliased rim is now a stair-step against whatever the transparent color resolves to. Keep PNG if the icon sits on varying backgrounds.
Frequently asked questions
Which size does the converter take out of the ICO?
The largest one stored in the file. An ICO commonly contains several renderings of the same artwork, 16, 32, 48 and sometimes 256 pixels, and only one can become the GIF. Taking the largest is the choice that keeps options open, because a big image can be scaled down later with reasonable results while a 16 pixel one cannot be scaled up at all.
Why did the smooth edge of my icon become jagged?
GIF stores transparency as a single bit per pixel: fully clear or fully opaque. Icon artwork is normally drawn with a soft anti-aliased rim where pixels are partly transparent, and there is no way to record that in a GIF. Those pixels have to become one or the other, which reads as a stair-step. PNG keeps the full alpha channel and is the better target when the edge matters.
Can I get an animated GIF out of an ICO?
No, and not because of a limitation here. An ICO holds multiple sizes of one picture, not multiple frames of a sequence, so there is no motion in the file to carry across. The output is a single-frame GIF. If you want animation you need a source that actually contains frames, such as an existing animated GIF or a video.
Further reading
- Half the Width and a Third of the Frames Took 60% Off the GIFThere are exactly three things that make a GIF smaller, and two of them are visible to the viewer. Knowing which one to spend first — and how much each is actually worth — saves a lot of guessing at a file that will not fit.
- GIF Transparency Has Exactly One Bit, and It Shows on Every EdgeA PNG can record a pixel as 37% transparent. A GIF cannot — each pixel is either fully visible or fully invisible, and there is nothing in between. On a shape with a soft anti-aliased edge, that difference is measurable, and it is why a logo saved as GIF gets a jagged fringe that no amount of care in the original file prevents.