Compress images to get under a size limit

How to hit a specific target size

Most people arrive here with a number in mind: a passport photo form wanting under 30 KB, a job portal wanting under 2 MB, a forum capped at 500 KB, an email attachment limit. Switch the tool to Target size and you can type that number directly:

1. Choose Target size, then pick a preset (20 KB up to 1 MB) or type your own limit in KB or MB.
2. Drop the files in and press Convert All.
3. Each file comes back at or under your limit — not exactly on it, since the limit is a ceiling. The result size is shown against every file.

Behind the scenes it searches for the highest quality that still fits, so you get the best-looking file the limit allows rather than an arbitrarily crushed one. If quality alone cannot get there, it shrinks the dimensions a step at a time and shows you the new width and height on that file. Files already under the limit are left untouched instead of being recompressed for no reason — except an iPhone HEIC, which is still turned into a JPG, and a photo whose metadata you have asked to remove.

The kept metadata counts towards the limit too. When capture date, camera and GPS are carried into a JPG, their bytes are included in the size check, so the downloaded file genuinely fits.

If you would rather steer it yourself, Quality mode still works the old way: convert, read the size, move the slider, convert again.

What 10 KB, 20 KB, 50 KB and 100 KB actually look like

The same 830 KB, 12-megapixel phone photo (3024×4032), run through Target size mode in Chrome with this tool:

From 100 KB upwards a modern phone photo fits at full resolution — only the JPG quality drops. Below about 50 KB there are simply too many pixels to describe in so few bytes, so the tool trades resolution for clarity instead of producing a full-size but smeared image. For the places that ask for 20 KB or less — exam and job application forms, ID photo uploads, signature fields — that is usually what they want anyway: those forms display the photo small, often only a few hundred pixels wide.

If a form also sets exact pixel dimensions (for example a fixed width and height for a passport-style photo), crop and resize to those first in any editor, then compress here. A smaller starting image reaches a small size limit at a higher quality.

What the quality slider actually does

It is not a percentage of the original size, and the relationship is far from linear. Measured on a 3024×4032 photograph with this tool:

Two things stand out. Dropping from 100 to 90 removes three quarters of the file for no visible cost at all, so quality 100 is essentially never worth using. And below about 60 the savings flatten out while the damage accelerates — from 60 to 30 you save only 56 KB but the image visibly falls apart. There is little reason to go below 60 unless you are desperate.

The honest limitation: a PNG kept as PNG rarely gets smaller

This is worth stating plainly rather than letting you discover it. If your file is a PNG and you keep it as a PNG, re-encoding it here will most likely make it larger, not smaller.

PNG is lossless, so there is no quality dial to turn — that is why the slider disappears when you select PNG. Real PNG optimisers shrink files by reducing the colour palette and applying smarter filtering, which a browser's built-in encoder does not do. In our test, a 7 KB screenshot re-encoded through the browser came back at 35 KB, because the source had been optimised and the browser's encoder had not. In Target size mode, a PNG that stays PNG can only get under the limit by having its dimensions reduced.

So to actually shrink a PNG, change format. In Target size mode, ticking Allow format change does this for you when needed — it switches the PNG to WebP, never to JPG, so transparency survives. Or pick the format yourself:

• Screenshots, diagrams, logos, anything with flat colour or transparency → convert to WebP. Our 7 KB screenshot stayed at 8 KB and our transparent logo went from 26 KB to 9 KB, with transparency intact.
• Photographs accidentally saved as PNG → convert to JPG. This is where the enormous wins are: 8,636 KB down to 337 KB in our test, a 96% reduction.

Where compression works best

Photographs are the ideal case. They are full of noise and gradual tonal change, which is precisely the kind of detail lossy compression can discard without your eye noticing. A camera photo will usually take a large reduction without complaint.

Images containing text are the difficult case. Screenshots, infographics, scanned documents and anything with fine lines degrade in a very visible way — letters develop a grey halo and thin lines go patchy. For these, keep the quality above 85 or switch format rather than compressing harder.

What this tool does not do

Being clear about the boundaries, since the biggest saving is often something else entirely:

• It does not resize to a size you choose. Quality mode never touches dimensions. Target size mode only reduces them as a last resort — in steps of about 20% of the area, and never below 200 pixels on the shorter side. If it still cannot reach your limit, you get the closest result, clearly marked as over target. If you need a specific width, such as 800 pixels for a website slot, resize in an editor first.
• It does not strip metadata to save space. Exif is a few kilobytes at most, so removing it is not a meaningful size lever. The metadata toggle exists for privacy, not compression — untick it if you're compressing something to share publicly, since GPS tags can reveal exactly where a photo was taken.
• It does not hit a size exactly. Your number is treated as a ceiling: the result lands at or under it, usually a little below, because encoders decide the final byte count based on image content.

Related conversions

• JPG to WebPUsually a bigger saving than compressing a JPG harder
• PNG to JPGThe single largest reduction available here
• HEIC to JPGConvert iPhone photos first, then compress