Pixels and file size are different things
An image’s dimensions (for example 4000 × 3000 pixels) say how much detail it holds; its file size (KB or MB) depends on the dimensions, the format and the quality setting. To get under an upload limit, first reduce the dimensions to what is actually needed, then lower the quality a little.
Which format?
- JPEG – photos. Quality 75–85% looks almost the same as the original at a fraction of the size. No transparency (see-through areas become white).
- WebP – usually the smallest file for the same look, with transparency. Most modern websites and apps accept it.
- PNG – screenshots, logos and graphics with sharp edges or transparency. No quality loss, but bigger for photos.
Worked example
A 4032 × 3024 phone photo of 3.2 MB needs to be under 500 KB for an online form. Setting the width to 1600 px keeps the shape (height becomes 1200 px); saving as JPEG at 80% quality typically gives a file of a few hundred KB – check the new size shown above before you download.
Common sizes
- Website images: 1200–1600 px wide is plenty for most pages.
- Email attachments: 1024–1600 px wide.
- Official uploads (visa, passport, job portals): follow the exact pixel size and file-size limit the website gives.
Privacy
The image is opened, resized and saved by your browser. Nothing is sent to a server, so it is safe for ID photos and documents. Location and camera data (EXIF) are not copied into the new file.
Quality setting explained
The quality slider controls how hard JPEG and WebP squeeze the picture. Around 80% is a good balance for photos; below about 60% you may start to see blocky patches around edges and in skies. PNG ignores the slider because it never loses detail. If a website rejects your file for being too big, lower the width first – halving the width cuts the number of pixels to a quarter.