Scaling changes the canvas pixel dimensions. Keep the aspect ratio locked for proportional resizing; enlarging does not recover detail missing from the source.
Original pixel grid
Same proportions at 150% scale
The finer grid illustrates more output pixels, not new image detail. Start from the clearest original available before enlarging.
Scale Image changes the width and height of the current canvas. Use Pixels when a destination requires exact dimensions, or Percent to scale both dimensions from the current image. The aspect-ratio lock is on by default; unlock it only when you deliberately want a different shape.
Leave Lock aspect ratio selected so width and height stay proportional. Unlock it only if you intentionally want to change the image shape.
No. Scaling resamples existing pixels and may soften edges; it does not reconstruct detail that is not in the source.
The tool uses your browser and device memory. Reduce the target dimensions if the browser cannot create the requested canvas.