What is QOI, the Quite OK Image format?
QOI came out of nowhere in late 2021 and developers loved it — a lossless image format whose entire specification fits on a single page. Here's what it is, why people use it, and how to actually open or create .qoi files.
Short answer
QOI (Quite OK Image) is a simple, lossless image format built for speed, not for the web. Nothing opens it by default, so to view or use a .qoi file you convert it: QOI to PNG. To create one for a game or tool pipeline, go the other way: PNG to QOI. Both run in your browser — nothing is uploaded.
QOI vs PNG at a glance
| QOI | PNG | |
|---|---|---|
| Lossless | Yes | Yes |
| Transparency (alpha) | Yes | Yes |
| Encode speed | Very fast (20-50x PNG) | Slower |
| Decode speed | Very fast (3-4x PNG) | Slower |
| File size | Similar to PNG (often slightly larger) | Smaller on average |
| Spec complexity | One page | Large |
| Browser / OS support | None | Universal |
Where QOI came from
QOI — short for "Quite OK Image" — was created by Dominic Szablewski in late 2021 out of frustration that lossless image codecs needed thousands of lines of code and heavy dependencies. His goal: a format simple enough that the entire spec fits on one page and a complete encoder and decoder fit in a few hundred lines of C. It's lossless, supports an alpha channel, and uses a single-pass algorithm with no entropy coding stage, which is what makes it so fast.
Why people actually use it
QOI's appeal isn't smaller files — it's speed and simplicity. It encodes roughly 20-50x faster than PNG and decodes 3-4x faster, with file sizes in the same ballpark (often a little larger than a well-optimized PNG). That trade is great when you're loading thousands of textures at runtime or want a dependency-free image format you can drop into a project. You'll mostly see it in game development, texture and asset pipelines, embedded and hobby projects — places where a programmer controls both ends and values fast, trivial code over maximum compression.
How to open or create a .qoi file
Because no browser, operating system, or mainstream image viewer supports QOI, a .qoi file won't open by double-clicking it. The fix is to convert:
- QOI to PNG — turn a .qoi back into a normal PNG you can view, edit, and share anywhere.
- PNG to QOI — encode a PNG into .qoi for your game or tool pipeline.
On ConvertBlink both conversions run entirely in your browser — the file never touches a server — and because QOI is lossless, a PNG → QOI → PNG round trip gives you back identical pixels.
Should you use QOI?
- Building a game or asset pipeline? QOI is a great fit if fast encode/decode and trivial code matter more than squeezing out every byte.
- Shipping images on the web? No — use WebP or AVIF (with PNG/JPEG fallback). Nothing on the web decodes QOI.
- Just received a .qoi file? Convert it to PNG and move on.
- Need the smallest lossless file? Optimized PNG (or lossless WebP/JXL) usually beats QOI on size.
FAQ
What does QOI stand for?
QOI stands for "Quite OK Image". It's a lossless image format created by Dominic Szablewski in 2021, designed to be extremely simple and fast rather than to achieve the smallest possible file size.
What opens a .qoi file?
Almost nothing by default — no browser, operating system, or mainstream image viewer supports QOI natively. The simplest way to view one is to convert it to PNG, which opens everywhere. Some game engines and developer tools can read QOI directly.
Is QOI better than PNG?
It depends what you mean by better. QOI encodes and decodes far faster than PNG and its spec is tiny, which is great for runtime asset loading and simple code. But PNG usually produces smaller files and is supported everywhere. For the web, PNG (or WebP/AVIF) wins; for a fast in-engine pipeline, QOI can be the better tool.
Is QOI lossless?
Yes. QOI is fully lossless and supports an alpha channel, so converting PNG → QOI → PNG returns pixel-identical results. No image quality is lost.
Why isn't QOI supported in browsers?
QOI is young (2021) and was designed for developer pipelines, not web delivery, so browser vendors haven't added it — and likely won't, since WebP and AVIF already cover the web's needs. To use a QOI image on a website, convert it to PNG or WebP first.
How do I convert QOI to PNG?
Use a QOI to PNG converter. On ConvertBlink it runs entirely in your browser — drop the .qoi file in and download a PNG, with no upload to any server.