Bild-Resizer

No. Resizing runs on the browser canvas, entirely on your device. Batch resizing twenty photos is as private as resizing one.

Cover scales the image until it fills the target frame completely and crops the overflow from the center — the output is exactly the requested size. Contain scales the whole image to fit inside the target box without cropping, so the output keeps the original aspect ratio and may be smaller than the box in one dimension.

Naive one-step downscaling skips over pixels and causes aliasing — jagged edges and moiré patterns on fine textures. This tool downscales in successive halving steps with high-quality interpolation, which preserves detail much better on large reductions.

Yes, but enlarging cannot create detail that was never captured — expect some softness beyond about 1.5×. For big upscales a dedicated AI upscaler produces better results than any pixel interpolation.

The presets cover the current standard dimensions for Instagram, X, YouTube, Facebook, LinkedIn and WeChat. Platforms occasionally change specs; the custom mode always lets you enter any exact size you need.