Resize an image to exactly 3840×2160 pixels
3840×2160 is the frame used for écrans 4K et exports pour l'impression. Drop a photo above and the editor opens with a resize step already set to those numbers — the only thing left to do is download. PIXLFLW runs the whole thing inside your browser: no upload, no queue, no account, and the picture never leaves your device.
Aspect ratio: 16:9
3840×2160 is a 16:9 frame. If your photo already has that shape, the resize is a clean scale and nothing is distorted. If it does not, forcing it into the frame stretches the picture — add a crop step first, pick the 16:9 preset, choose the part of the shot you want to keep, and then the resize lands on 3840×2160 in proportion.
Will it stay sharp?
Scaling down to 3840×2160 from a larger original is effectively lossless: high-quality resampling discards pixels smoothly and the result looks crisp. Scaling up is the harder direction — no tool can restore detail the camera never recorded, though enlargements up to roughly double the original still hold together. The editor shows the source dimensions next to the target so you always know which direction you are going.
Exact pixels and a file-size limit at once
Many upload forms cap both: 3840×2160 and a maximum weight in KB. Do the resize here, then switch on Target file size in the download dialog and type the limit — the encoder searches for the best JPEG quality that still fits and reports the real byte count before you save.
Formats and cost
JPG, PNG, WEBP, GIF and HEIC go in; JPG, PNG, WEBP or GIF come out. Free, unlimited, no watermark and no sign-up — resize one image or fifty, one after another.