Big files slow pages and hit upload limits. You can usually shrink them a lot with no visible quality drop.
1. Pick the right format
For photos, JPG or WEBP beats PNG; WEBP is ~25–35% smaller than JPG. See the format guide.
2. Tune quality
Around 0.85 is indistinguishable for most photos but much smaller.
3. Resize to what you need
Scale down to the display size — often the biggest saving.
Do all three in one pass in the converter.