Images are almost always the heaviest part of a web page and the slowest to load. Compressing them well can cut their size by 60-80% with no visible difference. This guide shows you how, which format to choose and why it's better to do it in your browser rather than on a site that uploads your files.
Lossy vs lossless compression
There are two broad types of compression:
- Lossy: discards information the eye barely perceives. This is JPEG and WebP. It allows huge size reductions with minimal visual loss if you pick the level well.
- Lossless: reduces size without throwing away any data; the image is identical to the original. This is PNG. It compresses less, but keeps 100% of the quality and transparency.
The key is using the right type for the image.
Which format to choose
| Format | Best for | Transparency | Size |
|---|---|---|---|
| JPEG | Photos | No | Low |
| PNG | Logos, screenshots, transparency | Yes | High |
| WebP | Almost everything on modern web | Yes | Very low |
- WebP usually gives the smallest size with good quality and all modern browsers support it. It's the best choice for the web today.
- JPEG is still the universal king for photos when you need maximum compatibility.
- PNG only when you need transparency or a perfectly crisp screenshot.
The optimal quality level
In JPEG and WebP, the quality control runs from 0 to 100. The sweet spot for most photos is 70-80: there you get big savings with a practically imperceptible visual difference. Below 60 artifacts start showing; above 90 the savings are small.
A good workflow: start at 75, look at the result and the size, and adjust. There's no universal magic number — it depends on the image.
How to compress images in batch
If you have many images (product shots, a gallery, a blog), compressing them one by one wastes time. Batch compression lets you:
- Upload or drag several images at once.
- Choose a common quality level (and optionally convert format).
- See the savings for each one.
- Download them all together in a ZIP.
You can do it for free with the image compressor on this site, which compresses everything in your browser with the Canvas API.
Why compress locally and upload nothing
Many compression sites upload your images to their servers. That means waiting for the upload, depending on their connection and handing over your files. When compression happens in your browser:
- It's instant (no upload or server download).
- Your images never leave your device.
- There are no quota limits or sign-up.
For personal photos or unreleased company material, this matters.
Impact on SEO and performance
Google uses load speed as a ranking factor (Core Web Vitals). Lighter images mean:
- Better LCP (Largest Contentful Paint), one of the key metrics.
- Less data usage for your visitors, especially on mobile.
- Pages that feel faster, which reduces bounce.
Compressing images is one of the highest-impact, lowest-effort optimizations there is.
Frequently asked questions
Is the quality loss noticeable? At a level of 70-80 in JPEG/WebP, practically no. PNG loses nothing.
Can I convert format while compressing? Yes. Converting a heavy PNG to WebP usually saves a lot while keeping transparency.
Is there a size or count limit? None imposed by the tool; it only depends on your device memory.
Do I lose EXIF metadata? Recompression usually strips it, which actually improves your photos' privacy.
Cut your images' size without sacrificing quality with the free image compressor: in batch, with ZIP download and 100% in your browser.