Compress Images Without Losing Quality: A Practical Guide

A photo straight from a phone or camera can weigh 4 to 10 MB, far too much for a web page or an email attachment. The good news is that most images can shrink dramatically without anyone noticing a difference. The trick is knowing which settings matter and in what order to apply them.

The short answer

• Resize first. Reduce the pixel dimensions to what you actually need. This usually saves more than any quality setting.
• Then compress with a quality of about 75 to 85 for JPG and WebP. Below that, artifacts start to show; above it, the file grows quickly with almost no visible gain.
• Pick the right format. Photos suit JPG or WebP, graphics with flat colors and sharp edges suit PNG or lossless WebP.

Do these three things and a 6 MB photo often ends up under 300 KB.

Lossy vs lossless

Lossless compression rewrites the file more efficiently without changing a single pixel. PNG is always lossless. The savings are modest, typically 10 to 30 percent, and depend on the image.

Lossy compression discards detail the eye is unlikely to notice. JPG and lossy WebP work this way. Savings are much larger, but the loss is permanent: every time you save again at a lower quality, you throw away more.

For photographs, lossy is almost always the right call. For screenshots, logos and diagrams with text, lossless keeps edges crisp.

Step by step

• Check the target size. A full-width hero image rarely needs more than 1600 to 2000 pixels across. A blog illustration is fine at 800 to 1200. An email photo is comfortable at 1200 pixels on the long side.
• Resize with Resize Images. Keep the aspect ratio locked so nothing looks stretched.
• Compress with Compress Images. Start at a quality around 80 and compare the result with the original at 100 percent zoom.
• Lower it gradually. If you see no difference, try 75. Stop as soon as you notice blocky patches or fuzzy edges around text, then go back up a step.
• Keep the original. Always work on a copy so you can re-export later from the untouched file.

Why the 75 to 85 range

JPG quality is not a percentage of anything physical. It is a scale that controls how aggressively detail is rounded off. Between 100 and about 85 the file size drops steeply while the image looks the same. Between 85 and 75 it still drops noticeably with very little visible change in photos. Below roughly 70, gradients such as skies and skin begin to show banding and blocks. The exact sweet spot varies by image, so treat the range as a starting point, not a rule.

Consider WebP or AVIF

Modern formats compress better than JPG at the same visual quality. WebP files are commonly noticeably smaller than equivalent JPGs and are supported by all current browsers. AVIF can be smaller still, but encoding is slower and support in older software is patchier.

If your images are for a website, converting with JPG to WebP or PNG to WebP is often the single biggest win. If you receive an AVIF or WebP and need something universally compatible, WebP to JPG does the opposite.

Tips and pitfalls

• Do not recompress repeatedly. Each lossy save adds artifacts on top of the last. Always export from the original.
• PNG photos are wasteful. A photograph saved as PNG can be five to ten times larger than a JPG. If transparency is not needed, PNG to JPG cuts the size sharply.
• Metadata adds weight. Camera data and embedded previews take space and may include location. Many compressors drop them; check whether yours does if privacy matters.
• Beware of screenshots of text. Heavy JPG compression produces halos around letters. Keep these as PNG.
• Do not upscale. Enlarging a small image and compressing it does not add detail, only size.

When not to recompress

Skip compression when the file is already small, around 100 KB or less for a web image, since further savings are tiny and the risk of visible damage is real. Also avoid it for images you will edit further, print at large sizes or archive. Keep a high-quality master and produce compressed copies only for delivery.

A quick rule of thumb

Ask three questions in order. Is it larger than it will ever be displayed? Resize. Is it a photo? Use JPG or WebP at roughly 80. Is it a graphic with sharp edges or transparency? Use PNG or lossless WebP. Conversions on Azpy run in your browser for local tools, so your images are not uploaded just to shrink them.