Resize image files by pixels, percent, or side

Resize image files when a slot, a layout, or a longest edge is the constraint. You can set pixels, a percent, or the longest side. Lock aspect starts on. Fit starts as inside the box. Do not enlarge starts on, so a small file is not blown up. Output can stay as it is, or become JPG, PNG, or WebP. The bitmap is resampled with Lanczos.

Illustration of a resize image frame scaling a photo by its longest side

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or drop / paste

How to resize image dimensions

Add a JPG, PNG, or WebP. Drop, paste, or Choose files. You can add more than one, up to one hundred, and the same rule is applied to each.
Choose pixels, percent, or longest side. Pixels use the width and height fields. Percent scales both edges from the current size. Longest side sets the longer edge and scales the other to match.
Leave Lock aspect on unless you mean to stretch. Leave Fit on Fit inside for a file that must sit inside the box. Choose Crop to cover or Pad to exact size only when you need those shapes.
Leave Do not enlarge on so a picture that is already smaller than the box stays at its own size. Turn it off only when you truly want upscaling.
Pick Keep, JPG, PNG, or WebP. Leave DPI at 0 unless you need a density tag. Press Resize images. DPI writes JFIF density or a PNG pHYs chunk and does not add pixels.

Resize image options explained

Resize by pixels, percent, or longest side. Percent defaults to 50 in the field, longest side defaults to 1920, and the pixel fields start at 1080 by 1080. The mode you pick is the one that is applied. The other numbers wait.

Lock aspect defaults to on. Fit inside keeps the whole picture inside the box. Crop to cover fills the box and center-crops whatever does not fit. Pad to exact size letterboxes the picture on a pad colour that defaults to #ffffff.

Do not enlarge defaults to on. If the calculated box is larger than the source, the output stays at the source size instead of inventing pixels. Turn it off when a small icon must become a larger bitmap.

Output defaults to Keep, or you can pick JPG, PNG, or WebP. Quality defaults to 80 for the encode. DPI defaults to 0, which skips density. A non-zero DPI writes JFIF density on JPEG or a pHYs chunk on PNG. It does not change the pixel count. Resampling uses Lanczos.

Three ways to name the size

Pixels are the right mode when a template says 1200 by 800 or some other pair. With Lock aspect on and Fit inside, the picture is scaled so both edges land inside that box, and one edge may come out shorter than the number you typed. That is the lock doing its job, not a missed field.

Percent is easier for a stack of similar photos you want at half size. Longest side is easier when orientations differ: a 1920 longest side makes every landscape and portrait share the same long edge without you swapping width and height by hand.

Fit inside, cover, and pad

Fit inside never cuts the picture. Empty space is simply a smaller result, not a border, unless you chose pad. Crop to cover is a center crop: the box is filled, and the parts that stick out past the center are discarded. Use it when a square avatar must be full, and check the edges.

Pad to exact size makes the width and height you asked for, and paints the spare margin with the pad colour, default #ffffff. That is how you get a true 1080 by 1080 from a portrait photo without cutting the head off. Change the colour if white would show as a mistake on a dark page.

DPI tags and the Lanczos resample

DPI does not add pixels and does not change how large the bitmap is. On a JPEG it writes JFIF density. On a PNG it writes a pHYs chunk. Leave it at 0 if you do not have a print workflow that reads that tag. A 300 DPI tag on a 800 pixel photo does not become a larger photo.

The resample is Lanczos. Edges stay cleaner than a crude stretch, and a big shrink still throws away detail you cannot get back from the download. Do not enlarge, left on, refuses to scale a small file up into a soft blur. Quality 80 applies when the pixels are encoded to JPG or WebP.

Common targets

Limits, formats and output

Accepted input	JPEG, PNG, WEBP, GIF, BMP, HEIC, AVIF
Files per batch	1–100
Soft size warning	50 MB each
Hard stop	500 MB total in memory
Output	The chosen image format, or a ZIP for a batch
Account	None. The tool runs in this tab.

Your file never leaves your device

This image is resized by code running in this browser tab. The work runs in a Web Worker in this tab, using WebAssembly for the heavy parts, and the result comes back as a local blob. This site does not upload the file, store it, or log its name.

To verify: load the page, turn on airplane mode, and drop the file again. It still finishes. Or open DevTools, choose Network, and watch the run: there is no upload. The architecture is described on How it works.

Frequently asked questions

Will resize image upscale a small file?

Not while Do not enlarge is on, which is the default. The output stays at the source pixel size when the box is larger. Turn the toggle off only if you accept a softer picture. Upscaling cannot recover detail the file never had.

What does crop to cover cut?

It center-crops. The box is filled edge to edge, and the overflow is taken equally from both sides of the longer dimension. Faces near the edge of a portrait can be clipped. Use Fit inside or Pad if the whole subject has to remain.

Does 300 DPI make more pixels?

No. DPI writes JFIF density on a JPEG or a pHYs chunk on a PNG. The pixel width and height come from the resize mode, the fit, and Do not enlarge. Zero DPI means do not write a density tag at all.

Does lock aspect ignore my height?

With Fit inside, both numbers are a box. The picture keeps its ratio and lands inside that box, so one side may be shorter than the typed value. Pad to exact size is what forces both numbers, using a margin colour. Cover forces both by cutting.

Can the format stay the same?

Yes. Keep follows the file: PNG stays PNG, WebP stays WebP, and other files go out as JPEG. Pick JPG, PNG, or WebP when the next tool demands one of those. Quality 80 is the encode setting for JPEG and WebP.

Is a folder a different tool?

This page already applies one rule to every file you add, up to one hundred, and offers a ZIP when more than one download is ready. Bulk resize images is the same engine, written for that batch job. Use either when the geometry is what you came for.

Last updated 2026-09-26. By Tam.