"Compress without losing quality" is slightly misleading — some compression is always a trade-off. But the human eye is forgiving, and with the right approach you can cut file sizes by 60–80% with no visible difference. Here is how, in the order that gives the biggest wins first.
1. Resize before you compress
The single most common mistake is serving a 4000-pixel-wide photo in a slot that displays at 800 pixels. The browser downloads the whole thing and shrinks it. Resize the image to the largest size it will actually be shown at — this alone often removes most of the weight.
2. Choose the right format
A photo saved as PNG can be many times larger than the same photo as JPG or WebP. Match the format to the content: lossy (JPG/WebP/AVIF) for photos, lossless (PNG/WebP) for graphics. Converting PNG photos to WebP frequently halves their size instantly.
3. Tune the quality setting
JPG and WebP let you pick a quality level. For most photographs, a quality of 75–85 is indistinguishable from the original at a fraction of the size. Below about 70 you start to see blocky artefacts. Experiment: drop the quality until you can just notice a difference, then step back up one notch.
4. Strip metadata
Photos carry hidden metadata — camera model, GPS location, colour profiles, thumbnails. Removing it shaves kilobytes and protects your privacy, with zero effect on how the image looks.
5. Use lossless optimisation on graphics
For PNGs and graphics you don't want to touch visually, lossless optimisers re-encode the file more efficiently — same pixels, smaller file. It is free size with no downside.
Putting it together
Resize → convert to WebP → set quality around 80 → strip metadata. That four-step routine handles almost every image and typically produces the smallest file that still looks great.