Why a website app needs six copies of one icon
When you make a website into an app, the icon is the first thing that stops being "the website's". A browser shows one favicon; Android shows your icon on home screens at five pixel densities, in a round variant on some launchers, as a two-layer adaptive icon on Android 8 and later, and at 512×512 on your Play Store listing. Each is a separate file in a separate folder, and Android picks the one that matches the phone. Give it only a small one and it upscales — which is the blurry-icon look of cheap apps.
This generator takes one square image and produces the whole set: mipmap-mdpi at 48 px through mipmap-xxxhdpi at 192 px, the round versions, and the Play icon. Every size is downscaled from your source, so start with at least 512×512 and ideally 1024×1024.
Padding, background and corners
Background fills behind a logo that is not square, or a PNG with transparency, so you do not get a transparent launcher icon that turns whatever colour the launcher paints behind it. Match it to your website's brand colour and the app is recognisably the site.
Padding shrinks the artwork inside the canvas. Adaptive icons are masked to a circle, squircle or rounded square depending on the phone, and only the centre is guaranteed visible; 10–15% padding keeps a logo that touches the edges from losing its corners. Corner radius rounds the legacy icon used by older launchers. Leave it at 0 for the adaptive foreground — Android masks that itself, and pre-rounded artwork gets rounded twice.
Designing for a home screen, not a header
Your site's logo was drawn for a header at 200 px wide, usually with the name beside it. At 48 px on a budget phone the name is unreadable and the mark is a few dozen pixels. What survives: one shape, strong contrast, no thin lines, no text — the launcher writes the app name underneath anyway. If your logo is only a wordmark, use its first letter on your brand colour. Shrink your candidate to 48 px and look at it from arm's length before you commit; the icon guide has the full checklist.
The builder does this step for you when you make your app — you upload one image and it generates the set. Use this tool when you want to see the output first, tweak padding for a difficult logo, or produce a set for a project you are building elsewhere.