Index
Guides to compression
The tool prints numbers. These pages exist for the two occasions when the number on its own points the wrong way.
A ledger can say that a file went from 4.2 MB to 180 KB, and it can say that a file went from 812 KB to 806 KB and was therefore left out of the download. What it cannot say is which of those outcomes was decided long before you arrived. Both pieces below are about that: the moment where the answer is arithmetic rather than a setting, and where knowing the arithmetic first saves you from a run that was never going to work.
Each one is written about the mechanisms this page actually runs rather than about the format specifications, each states where the tool gives up, and neither is long enough to need skimming.
The two pieces
Why this JPEG will not get smaller
One division — file size over pixel count — tells you whether there is anything left to take, before you spend an afternoon moving a quality slider that cannot help.
Read it if: A compressor reported a three percent saving and you assumed it was broken. · about 7 minutes
Upload limits on Indian exam portals
A form asking for 20 KB and 200 by 230 pixels is asking two separate questions, and answering them in the wrong order costs you the photograph twice over.
Read it if: A portal rejected your upload and the message did not say which rule you broke. · about 9 minutes
What is not written up here, and why
There is nothing on WebP or AVIF, because this build reads those formats and does not write them — a guide to settings the tool cannot offer would be an advertisement for some other program. There is nothing on metadata beyond the itemised list the ledger already prints, because the whole story is one sentence: a re-encode rebuilds the file from pixels and every block goes. And the exam-portal figures are the part of this site most likely to drift: they are bands read off published forms rather than a rule, they carry no promise of being current on the day you read them, and a correction is more welcome than a compliment.
Or go straight to the tool
- Compress an imageAll three mechanisms, the file queue, and the 400 percent comparison.
- Compress to a size in KBIf the exam-portal guide is the one you came for, this is the page it ends at.
- Compress a JPEGIf the quantisation-floor guide is the one you came for, this is where you test it.