How to Reduce a Photo's File Size: Resize First, Then Compress

A photo straight off a modern phone is routinely 3–5 MB. Drag the quality slider on a compressor and it might drop to 1–2 MB. Resize it down to a sensible size first, and it can fall well under a megabyte — often smaller than compression alone manages, and with less visible quality loss. The reason comes down to two separate things that both make a file "big," and most compressors only touch one of them.

Pixel count and quality are two different levers

A JPEG's file size is driven by roughly two independent factors: how many pixels it has (its width × height), and how much detail is kept per pixel (the quality/compression setting). A 4000×3000 photo has 12 million pixels to store, however lightly you compress it. Turning that into a 1600×1200 image cuts it to 1.9 million pixels — about a 6x reduction in pixel count before a quality slider is even touched. Compression quality, by contrast, controls how much fine detail JPEG throws away per pixel — it can't reduce how many pixels there are.

What the Image Compressor actually does

Image Compressor only touches the second lever. It draws your image onto a canvas at its original width and height, unchanged, and re-encodes it as a JPEG at whatever quality (10–95%) you choose — the pixel dimensions never change. That's exactly why resizing first matters: if your photo is already far larger, in pixels, than it needs to be, compression alone is working with a handicap it can't remove.

One implementation detail worth knowing: this tool always saves as JPEG, even if you uploaded a PNG. If that PNG had transparent areas, they don't survive — the tool draws onto a plain canvas with no background fill, so transparent pixels come out solid black in the JPEG, not white. If you need to keep transparency, don't run it through the compressor; if you need to flatten a transparent PNG to a filled background instead, use the Image Format Converter, which explicitly fills transparent areas with white before converting to JPEG.

Resize first, then compress

Resize Image changes the actual pixel dimensions — type an exact width and height (or drag a corner handle), with an option to lock the aspect ratio so you don't stretch the picture. Do this before compressing, not after: once an image is downscaled, a quality setting has far less data left to discard, so it takes a much smaller file to look the same.

Run through the same steps on a test photo (a synthetic 4032×3024 image, not a real camera photo, so treat the numbers as illustrative rather than a guarantee for your own photos):

Resizing alone beat quality compression alone here, and doing both took it further still. The exact percentages depend heavily on what's actually in a photo — a busy, detailed scene compresses less than a simple one — but the ordering effect (resize before you compress) holds generally, because it addresses the bigger of the two numbers first.

JPEG vs PNG: pick the one that fits the content

JPEG uses lossy, quality-adjustable compression built for photos — continuous tones and natural detail compress well, and a little quality loss is hard to see. PNG is lossless and better suited to screenshots, logos, and graphics with flat colors and sharp edges — the kind of image where JPEG's compression tends to introduce visible blotching around hard edges. PNG also has no quality slider to speak of; a photo saved as PNG is usually far larger than the same photo as a reasonably-compressed JPEG, for a difference you likely can't see. Use the Image Format Converter to switch between PNG, JPEG, and WebP if you're not sure which you have, or need one specifically for transparency (PNG or WebP; not JPEG).

A quick removable extra: metadata

Photos from phones and cameras often carry EXIF metadata — GPS coordinates, device model, timestamp — that adds a little to the file size and, more importantly, can reveal more than you intend if the photo is shared publicly. EXIF Data Remover strips this out; it won't be your main lever for a big size reduction, but it's a sensible step before sharing a photo online regardless.

Reaching a specific size limit

• Resize to the dimensions you'll actually display or need — a photo for a web page or a form upload rarely needs to exceed about 1500–2000 px on the long edge.
• Then compress, starting around 70–80% quality and adjusting from there based on the before/after size shown.
• Still too large? Resize smaller still — dropping from, say, 1600 px to 1200 px on the long edge cuts the pixel count by close to half again.
• Check it still looks right at the size you'll actually view or print it — a photo can look perfectly sharp on a phone screen at a resolution that would look soft printed at full page size.

What these tools don't do

• Neither tool batch-processes — each runs on one image at a time.
• Image Compressor can't reduce dimensions, and Resize Image doesn't have a JPEG quality slider — for both effects, run one after the other, in that order.
• There's no "hit an exact KB target" mode in either tool — you're adjusting dimensions and quality and checking the result, not entering a target size directly.

If your target photo is destined for a PDF rather than staying a standalone image, the same resize-before-compress idea carries over — see Image to PDF once your photos are the right size.