How On-Device Image Upscaling Works
What this upscaler does
This tool enlarges a raster image to double (2x) or quadruple (4x) its pixel dimensions. Instead of simply repeating existing pixels, it calculates every new pixel from a weighted average of its neighbours, which keeps edges crisp and gradients smooth rather than turning them into visible blocks or jagged staircases. The 4x setting does this in two steps.
An optional Sharpen edges pass then runs over the enlarged result, lifting edge contrast so the output reads as clearer rather than merely bigger.
When to reach for it
Upscaling earns its keep whenever a source image is simply too small for where it needs to go: a product thumbnail destined for a full-width banner, an old profile picture, a tightly cropped photo, or a low-resolution screenshot. Choose 2x when you need a fast, moderate size boost, and 4x when the original is tiny and requires a dramatic enlargement.
A concrete example
Feed in a 500x500 image and 2x returns 1000x1000, while 4x returns 2000x2000. The dimensions of both the original and the result are shown side by side, so you can confirm the new size before downloading. Turning on Sharpen edges for that same 500x500 source recovers noticeably more edge definition than the plain enlargement.
Formats, limits, and what to expect
Inputs can be JPG, PNG, or WebP up to 10MB, and you can save the result as PNG -- which preserves transparency and maximum quality -- or as JPG for a smaller file. To keep processing responsive, an image whose longest side exceeds 1024 px is first scaled down to that size and then enlarged from there. Bear in mind that enlarging fills in new pixels from the ones that are already there; it cannot recover detail that a heavily blurred or compressed original never recorded.