How to Compress an Image Without Losing Noticeable Quality

Your image is too big. The email bounced, the CMS rejected it, or Google PageSpeed is flagging it as a problem. This page explains how to fix it and what's actually happening when you do.

When You'd Need This

Web developers spend a lot of time on this. Images are consistently the largest assets on a page, and they're the easiest thing to fix. Core Web Vitals, specifically Largest Contentful Paint (LCP), are directly affected by image weight. A 3MB hero image that could be 400KB is a concrete problem, not an abstract one. Compressing it to a reasonable quality level is often the highest-ROI performance fix you can make.

It also comes up outside of web work more than people expect. Gmail and Outlook both cap attachments at 25MB. If you're sending a batch of product photos or client deliverables, you hit that ceiling quickly. Compressing to 80% quality typically cuts file size by 60–70% with no perceptible quality difference to a non-photographer.

Social platforms add their own constraints. Instagram, Twitter/X, and LinkedIn all have upload limits and often re-compress your image anyway. If you compress it yourself first, you control the quality. Letting the platform do it means accepting whatever their encoder decides.

How to Do It

1. Open the Image Compressor in your browser.
2. Drop your JPG, PNG, or WEBP file onto the upload zone, or click to select it from your device.
3. Adjust the quality slider. Start at 80 if you're unsure; that's the most common sweet spot for web use.
4. Click Compress and download the result. Check the file size and preview before you ship it.

If the result is too large, nudge the slider down to 70. If it looks degraded, nudge it back up. The preview updates so you can see what you're committing to.

What's Actually Happening

JPG compression works by dividing your image into 8x8 pixel blocks and running a Discrete Cosine Transform (DCT) on each one. This converts pixel data into frequency information — essentially "how fast do colors change across this block?" A quantization table then rounds off the high-frequency data (fine detail, sharp edges) based on a quality parameter. Higher quality means less rounding. Lower quality means more. That's why the degradation shows up first in sharp edges and fine textures.

The "quality 80" sweet spot has real numbers behind it. A 5MB photo at quality 100 compresses to roughly 4.8MB — almost nothing changes. At quality 80, that same photo is typically 1.2–1.8MB, and the visual difference is invisible unless you zoom in and compare them side by side. At quality 60, you're looking at 600–900KB, and you'll start seeing blocky artifacts in gradients and around high-contrast edges.

PNG works differently. It's a lossless format, so the compressor can't throw away image data the way JPG does. Instead, it applies DEFLATE compression more aggressively and strips embedded metadata like EXIF tags, color profiles, and thumbnails. For a typical PNG, this might get you 10–30% reduction without touching a single pixel.

Compression Results by Quality Level

Quality Setting	Typical Size Reduction	Visual Quality	Best For
90–100%	5–20%	Indistinguishable from original	Print, archiving, source files
75–85%	50–70%	No visible difference at normal viewing size	Web use, email, social uploads
50–70%	70–85%	Slight softness; artifacts visible on zoom	Thumbnails, previews, low-bandwidth contexts
Below 50%	85–95%	Visible blocking and banding	Not recommended unless file size is the only concern

Your Files Don't Leave Your Device

The compressor runs entirely in your browser using WebAssembly. Product photos, client work, personal images: none of it is sent to a server because there's no server involved. The file goes from your disk to your browser's memory and back to your disk. That's the full path.