GIF's 256-Colour Limit and the Move to PNG

Where the number 256 comes from

To understand GIF you first have to understand how it stores data, because the format's entire character follows from that.

GIF is palette-based. Inside the file sits a colour table. Instead of carrying its own colour value, each pixel carries the index of an entry in that table. A pixel does not say "red"; it says "colour number 47 in the table."

That index is expressed with 8 bits per pixel. Eight bits can take at most 256 distinct values. So a GIF frame can contain at most 256 different colours.

This is not a quality setting or a compression preference. It is a hard limit baked into the format's data structure. You can choose which 256 colours make it into the palette — a green-heavy landscape gets a different palette from a blue-heavy seascape — but you cannot raise the count.

The two kinds of damage the limit does to photographs

For low-colour content like graphics and logos, 256 colours are more than enough. The problems start with photographs, because a typical photo contains tens of thousands of distinct colour tones. Reducing that to 256 produces two characteristic forms of damage.

Banding. In smooth gradients such as skies, skin tones and shadow transitions, the intermediate tones disappear. What should be a continuous transition turns into visibly separated bands of colour. You see this most clearly in a sunset photo.

Dithering. This is the compensating technique used to hide banding. Two palette colours are scattered together in a speckled pattern so that, from a distance, the eye reads an intermediate tone. It works from a distance, but it gives the image a grainy, speckled texture. Look closely or enlarge the image and the pattern becomes plainly visible.

Together, these two problems explain why GIF is a poor carrier for photographs. The format was never designed for them; it was meant for simple graphics, drawings and short animations.

What PNG fixes, and what it doesn't

PNG works with no palette limit. It can store RGB values directly for each pixel, meaning it can carry millions of distinct colours.

From that, people very commonly leap to the conclusion that "if I convert the GIF to PNG the colours will be fixed." Here is the truth:

PNG preserves the existing 256 colours perfectly. Nothing is lost in the conversion; the output is pixel-for-pixel identical to the original. That is the good news.

PNG cannot bring back the lost colours. When the source image was reduced to 256 colours during the GIF's creation, the tens of thousands of tones discarded at that moment were permanently gone. That information is simply not in the GIF file. PNG cannot read what is not there.

As a result, banding survives intact in the PNG output. The dithering pattern survives intact. The image does not become richer in colour; it has merely been moved into a more capable container.

The only route to genuine colour richness is to go back to the original source file the GIF was made from. If you still have it, produce PNG or WEBP directly from there — do not route through the GIF.

Transparency carries a similar limit

Alongside its colour limit, GIF has a transparency limit, and it works on the same logic.

GIF transparency is binary: a pixel is either fully transparent or fully opaque. There is no value in between. One colour in the palette is flagged as "transparent" and pixels carrying that colour become invisible. That is the whole mechanism.

The practical consequence is the staircase look on rounded and sloped edges. The edges of a logo GIF are always jagged, because the format does not allow a soft transition.

PNG's alpha channel, by contrast, can store 256 distinct levels of opacity per pixel. Smooth transitions from fully visible to fully invisible are possible.

But just as with colour, that capability does not work retroactively. PNG gives you the ability to produce soft edges; it does not automatically fix jagged edges inherited from the GIF. The partial-transparency information was never in the source file, and PNG cannot invent it.

So what does the conversion buy you?

The gain is not in repairing the past but in lifting the limits for what comes next.

Palette pressure ends. When you edit and save a GIF, every new colour you add strains the palette and the file is squeezed back down to 256 colours. Every save layers another reduction on top of the last. Once you convert the GIF to PNG, that pressure disappears; you can add as many colours as you like and save as often as you want.

Soft transparency becomes possible. You can clean up the edges by hand and create semi-transparent transitions. In GIF that was technically impossible.

Compatibility improves. Modern editors and systems open PNG directly as RGB. GIF's palette structure produces extra conversion steps and unexpected behaviour in some tools.

In summary

GIF's 256-colour limit is embedded in the format's data structure and shows up in photographs as banding and dithering. PNG does not carry that limit, but it also cannot produce colours that are not in the GIF you have. The conversion preserves the current image perfectly and removes the palette and transparency constraints from here on. If what you really want is the colours back, the place to look is not a converter but the original source file.