What does this tool do?

It enlarges (upscales) small images: by a zoom factor, or to a width or height you choose. Enlarging has to calculate the new pixels from the existing ones. How this is done (the interpolation filter) decides whether the result looks blocky, blurry or sharp. Because no filter suits every image, you get several results and choose the one you like best.

Which filter should I use?

• AI photo (Real-ESRGAN): a neural network trained on photos guesses how the larger image could look. Edges stay sharp and surfaces clean. It removes part of the noise and keeps some grain, so photos don't look painted.
• AI drawing (Real-ESRGAN anime): a network trained on drawings. It keeps outlines clean and colors flat: for drawings, comics, logos and graphics.
• Both AI results are only made for images up to 500 x 500 pixels.
• Lanczos is sharp and the best choice for most photos. At hard edges it can show thin light or dark halos.
• Mitchell is smoother, with fewer halos.
• Pixel art turns every pixel into a block with hard edges: for pixel art, icons and screenshots, which the other filters blur.

Can enlarging add details?

Not really: an enlarged image has more pixels, but no details that weren't in the original. The AI only invents plausible-looking ones. The larger the zoom factor, the softer the result looks. For prints, enlarging by a factor of 2 to 4 usually works well.

Limits

You can upload JPG, PNG, GIF and BMP images of up to 5 MB and 3000 x 3000 pixels (of an animated GIF, the first frame). The enlarged image can be up to 4000 pixels wide and high, as JPG, PNG or WebP. Transparent areas stay transparent in PNG and WebP and become white in JPG.