How to Compress Images for Websites, Email and Upload Forms
Last updated: 3 November 2026
A single phone photo is often 3–6MB — far more than a website, email or upload form needs. Three settings decide how small an image gets: its pixel dimensions, its format, and (for JPG) its quality. Here's how to use each one.
Why photos are so large
Modern phone cameras capture 12 megapixels or more — roughly 4000 × 3000 pixels. A website column or an email preview rarely displays an image wider than 1000–2000 pixels, so most of that data is never seen. File size grows with the number of pixels, so the biggest savings almost always come from reducing the dimensions, not from fiddling with quality.
The three settings that matter
Dimensions: halving the width and height leaves a quarter of the pixels, and the file shrinks dramatically. In Compress Image, set a maximum width — the height scales to match.
Format: JPG is built for photographs and is usually far smaller than PNG for the same photo. PNG is lossless and suits screenshots, logos and anything with transparency.
Quality (JPG only): a quality around 70–80 typically looks the same as the original at normal viewing size. Below about 50, blocky artefacts start to appear around edges and in smooth areas like skies.
Settings that work for common jobs
Website or online store photos: maximum width around 1600–2000 pixels, JPG, quality 75–80.
Email attachments: maximum width around 1200–1600 pixels, JPG, quality around 75.
Strict upload forms (e.g. a 200KB or 1MB limit): reduce the width first, then lower the quality step by step until the file fits.
Logos, icons and screenshots: keep PNG, and reduce the width if the image is larger than it will be displayed.
Why a PNG didn't get smaller
PNG compression is lossless, so there is no quality setting to lower — re-saving a PNG at the same size often produces a file of almost the same size. To shrink a PNG, reduce its maximum width, or, if it's a photo without transparency, save it as JPG instead. Converting a transparent logo to JPG would fill the transparent areas with white, so keep those as PNG.
Things to know before you compress
Keep your original. Compression can't be undone, and re-compressing an already-compressed JPG adds new artefacts each time.
Re-saving an image removes embedded metadata such as the camera model and the GPS location where a photo was taken — usually a privacy benefit when you're posting photos online.
Compress Image runs entirely in your browser, so your photos are never uploaded.