50 KB needs smaller dimensions
At 50 KB, the pixel size matters more than the quality slider. A 600 × 600 JPG fits comfortably; a 3000 × 4000 photo would turn into a blurry mess. When you don’t set dimensions, Zekoya automatically lowers them until good quality fits in 50 KB, and tells you the final size.
Forms that also have a minimum
Some forms say “between 20 KB and 50 KB”. Choose “Range” under File size and enter both numbers. If the image is too simple to reach the minimum even at maximum quality, Zekoya adds neutral padding to the JPG so the file is accepted — and tells you it did.
Questions
Why JPG by default?
Upload forms with 50 KB limits almost always ask for JPG/JPEG. You can switch to WebP or PNG.
Is the quality reduced a lot?
Only as much as needed. The result screen shows the quality used and warns you if compression had to be heavy.