Image transparency and alpha channels, explained
Transparency is the single most misunderstood property of an image file. A logo that looks perfect on a transparent canvas suddenly grows a white box when it lands in the wrong format, and the cause is almost always the same: the destination format has no alpha channel. This guide explains what an alpha channel is, which formats carry one, and how to convert between them without flattening your transparency — all in your browser, with no upload.
Open the converter →Which image formats support transparency?
PNG, WebP, and AVIF all support full transparency. WebP supports it in both lossy and lossless modes, AVIF supports a high-quality alpha plane, and PNG stores an 8-bit alpha channel losslessly. GIF supports only 1-bit transparency — a pixel is either fully visible or fully invisible. JPG has no alpha channel at all and cannot be transparent.
What an alpha channel actually is
A normal colour image stores three channels per pixel: red, green, and blue. An image with transparency adds a fourth channel — alpha — which records how opaque each pixel is. In the common case, alpha is an 8-bit value from 0 to 255, where 0 is fully transparent (the pixel is invisible and whatever sits behind it shows through), 255 is fully opaque, and every value in between is partially see-through. This per-pixel grading is what makes soft drop shadows, feathered cut-outs, anti-aliased text, and faded gradients possible. A logo edge that fades smoothly from solid colour to nothing is not a hard mask; it is a row of pixels with alpha values stepping down from 255 toward 0. There are two ways an RGBA pixel can store its colour relative to its alpha, and the distinction matters when transparency goes wrong. In straight (non-premultiplied) alpha — what PNG uses — the red, green, and blue values are the pixel's true colour, independent of its opacity, and alpha is recorded separately. In premultiplied alpha, the colour channels have already been multiplied by the alpha value, which is convenient for fast compositing on the GPU but can produce dark fringes around edges if software later treats the values as straight. Most file formats, including PNG, store straight alpha; premultiplication is usually an internal detail of rendering engines. The practical takeaway is that a correct converter must carry alpha through as its own channel and never bake it into the colour or composite it against an assumed background. The reason JPG can never be transparent is structural, not a limitation that better encoding could fix. JPEG was designed for continuous-tone photographs and stores only luminance and two chrominance channels — there is simply nowhere in the format to put a fourth alpha value. Any tool that "saves a transparent image as JPG" is really compositing your image onto a solid background first, almost always white, and discarding the alpha channel in the process.
Transparency support by format
How the five most common web and design formats handle transparency. "8-bit alpha" means 256 levels of opacity per pixel, the kind that produces smooth soft edges.
| Format | Transparency support | Notes |
|---|---|---|
| PNG | Yes — full 8-bit alpha | Lossless. The universal choice for transparent logos, icons, and cut-outs; opens everywhere with no plugin. |
| WebP | Yes — full 8-bit alpha | Works in both lossy and lossless modes. Smaller than PNG at equivalent quality; supported in all current browsers. |
| AVIF | Yes — full 8-bit alpha | Alpha is encoded as a separate plane and can be lossy or lossless. Smallest files, but weaker support in design and print tools. |
| GIF | Yes — 1-bit only | A pixel is either fully visible or fully invisible. No soft edges; transparent boundaries look jagged on non-matching backgrounds. |
| JPG | No | No alpha channel exists in the format. Transparent areas are flattened onto a solid colour — almost always white — on export. |
Why backgrounds turn white
The classic failure looks like this: you have a transparent PNG logo, you save or export it as JPG to make the file smaller, and the transparent area comes back as a solid white rectangle. Nothing is broken — this is exactly what the JPG format requires. Because JPEG has no alpha channel, the software has to decide what colour the transparent pixels should become, and the near-universal default is white. The alpha information is gone the moment the file is written, and no amount of re-editing the JPG can recover it. The same thing happens, more subtly, when a soft drop shadow gets a hard white halo: the semi-transparent shadow pixels were composited against white and then frozen. The fix is to keep your image in a format that actually has an alpha channel. Converting a transparent PNG to WebP or AVIF preserves every alpha value and produces a much smaller file; converting a transparent WebP or AVIF back to PNG gives you a universally compatible transparent file for design tools, email, and print. The conversions on this site decode the source into a raw RGBA pixel buffer and write that exact buffer — alpha channel intact — into the destination format. PNG output uses oxiPNG, which writes the alpha bytes losslessly. WebP output uses libwebp with alpha compression enabled. AVIF output uses libavif, which encodes a dedicated alpha plane. The only conversion that discards transparency is converting to JPG, and that is the format's nature rather than a flaw in the tool — when you ask for JPG, the image is composited onto white because there is nowhere else for the transparent pixels to go. Everything runs as WebAssembly inside a Web Worker on your own device. There is no upload, no server, and no account; the codecs do the work on your CPU, and the app keeps working offline as a PWA after the first visit.
Transparency-preserving converters
Pick the conversion that matches your source and destination. Every one of these carries the alpha channel through unchanged — except the JPG path, which flattens transparency by design.
- WebP to transparent PNG — Decode a transparent WebP and write it to PNG with every alpha value preserved — for design tools and software that do not accept WebP.
- AVIF to transparent PNG — Turn a transparent AVIF into a universally compatible PNG, alpha plane intact, for Illustrator, print workflows, and older CMS platforms.
- PNG to WebP — Shrink a transparent PNG into a much smaller WebP while keeping full 8-bit alpha for the web.
- WebP to PNG — Convert WebP to PNG, transparency included, when you need the lossless, plugin-free format everything opens.
- PNG to JPG — Convert PNG to JPG for photographs and the smallest files — but note: JPG has no alpha, so transparent areas are flattened onto white.
FAQ
Can WebP be transparent?
Yes. WebP supports a full 8-bit alpha channel in both its lossy and lossless modes, so it handles soft edges, drop shadows, and feathered cut-outs exactly the way PNG does. At equivalent visual quality, a transparent WebP is typically much smaller than the same image as PNG, which is why it is a good choice for transparent assets delivered to the web. Every current browser decodes WebP transparency correctly.
Does AVIF support transparency?
Yes. AVIF stores transparency as a dedicated alpha plane, which can be encoded losslessly or lossily independently of the colour image, and it supports the same 256 levels of opacity per pixel as PNG and WebP. AVIF usually produces the smallest transparent files of any common format. The trade-off is tooling: many design applications, print workflows, and older content systems still cannot read AVIF, so converting a transparent AVIF to PNG is often necessary for non-web destinations.
Does JPG support transparency?
No. The JPEG format has no alpha channel — it stores only luminance and colour information for photographs. When you export a transparent image as JPG, the software composites your image onto a solid background colour first, almost always white, and discards the transparency. This is why a transparent logo saved as JPG comes back with a white box. If you need transparency, use PNG, WebP, or AVIF instead.
How do I make a transparent background?
Transparency has to be created in an image editor — you remove or erase the background so those pixels carry an alpha value of 0, then export to a format that supports alpha. Tools such as Photoshop, GIMP, Affinity Photo, or the background-removal feature in many apps can do this. Once you have a transparent file, save it as PNG, WebP, or AVIF. This converter does not erase backgrounds; it preserves the transparency an image already has when you change its format. If your source is already transparent in one format and you need another, the converters above carry the alpha channel through unchanged.
Why is my transparent image showing a white box?
Almost always because the image was saved or converted to JPG somewhere along the way. JPG cannot store transparency, so the format flattens transparent pixels onto a solid colour — white by default — and the alpha information is permanently lost. Re-saving that white-boxed JPG will not bring the transparency back; you need to go back to the original transparent source and convert it to PNG, WebP, or AVIF instead. A hard white halo around a soft shadow is the same problem on a smaller scale: semi-transparent edge pixels were composited against white.
Do these converters keep my files private?
Yes. Every conversion runs entirely in your browser using a battle-tested, browser-based codec stack compiled to WebAssembly inside a Web Worker — the codecs run on your own CPU. Your files are never uploaded to a server, there is no account, and the tool is free because there are no servers to pay for. After the first visit it also works offline as an installable PWA.