How to reduce image file size without losing quality

A photo from a modern phone weighs 3 to 8 MB and measures around 4000 pixels wide. That’s perfect for printing a poster — and far too heavy for a website, an email, an online form or a messaging app. The good news: you can usually cut the file size by 80–95% with no difference anyone will notice on screen. The trick is knowing which of the three levers to pull.

The three levers: dimensions, compression, format

Most people only touch compression. The biggest win almost always comes from resizing first.

Step 1: resize to the size you actually need

There is no point sending a 4032 × 3024 photo to someone who will view it on a phone 400 pixels wide. Useful targets:

With Resize Image, choose Resize by: Percentage, Width (px) or Height (px). The aspect ratio is kept automatically, so you only enter one value. You can also convert the format at the same time.

Step 2: compress at the right quality

JPG and WebP are lossy formats: they discard detail the eye barely perceives. The quality setting controls how much:

• 90–100%: very large files, no visible gain over 85%.
• 75–85%: the sweet spot for photos. Indistinguishable from the original on screen.
• 60–75%: fine for thumbnails and backgrounds.
• Below 60%: visible artefacts — blocky skies, halos around text.

With Compress Image:

1. Click Choose files or drop your images (JPG, PNG, WebP, AVIF, BMP — batches are fine).
2. Set Quality (75% by default) and, optionally, a Max width (px) to resize in the same pass.
3. Click Convert and download the results (Download all (ZIP) for batches).

Each image keeps its format, and the result is never larger than the original: if an image is already well optimized, you get it back unchanged. Everything runs in your browser — nothing is uploaded.

Step 3: pick the right format

Two conversions give big gains:

• Photo saved as PNG → JPG: often several times smaller. Use PNG to JPG (transparent areas become white).
• JPG or PNG → WebP for a website: typically 25–35% smaller than JPG at similar quality, with transparency support. Use JPG to WebP or PNG to WebP.

For a deeper comparison, see PNG vs JPG vs WebP: which format to use.

What “without losing quality” really means

Strictly speaking, only lossless operations keep every pixel identical: removing metadata, optimizing PNG encoding, or converting losslessly. They save little.

Everything that gives big savings — resizing, lossy compression — technically removes information. What matters is whether you can see it. At the dimensions an image is displayed and at 75–85% quality, you can’t. Two rules keep you safe:

1. Always work from the original. Re-compressing an already compressed JPG stacks losses. Keep your originals and export fresh copies.
2. Compress once, at the end. Crop, resize and edit first, then compress as the last step.

Built-in methods, if you prefer

Windows 11: in the Photos app, open the image, use the … menu > Resize image, choose a preset or custom size and save a copy. In Paint, Resize (Ctrl+W) then Save as.

Mac: in Preview, Tools > Adjust Size to change dimensions, then File > Export, choose JPEG and move the Quality slider. Finder’s Quick Actions > Convert Image also offers small, medium and large sizes.

iPhone: when you attach photos in the Mail app, you can choose a smaller image size before sending. For other uses, a Shortcut with the Resize Image action, or a browser tool, does the job.

Android: options depend on the phone brand’s gallery app (some offer “Resize” in the edit menu). A browser tool works the same on every phone.

These are fine for a few images. For batches, precise quality control or format conversion, a dedicated tool is faster.

Common scenarios

“The upload form says max 2 MB.” Resize to 2000 px wide and compress at 80%; a phone photo typically lands well under 1 MB.

“My website is slow.” Images are usually the heaviest part of a page. Resize to the displayed width (×2 for sharp display on high-density screens), serve WebP, and lazy-load images below the fold. Faster pages help both visitors and search rankings.

“I need to email 30 holiday photos.” Batch them through Compress Image with a max width of 1600–2000 px. Thirty photos at 300–600 KB each fit in a single 25 MB email.

“It’s a screenshot with text.” Keep it PNG, or use WebP. JPG blurs sharp text edges.

“It’s an iPhone HEIC photo.” Convert with HEIC to JPG first, then compress.

“It’s a PDF full of images.” Use Compress PDF instead — it re-encodes the images inside the document.

Quick checklist

1. Resize to the size you need.
2. Choose the format that fits the use (JPG for sharing, WebP for websites, PNG for graphics).
3. Compress at 75–85%.
4. Compare with the original at 100% zoom.
5. Keep the original file.