Guide
What a skip means
Every row on the desk ends with a code: what happened to that file and why. Here is each one, with what it means for your file and what, if anything, to do.
The codes
| Code | What it means | What to do |
|---|---|---|
| ok | A new copy was written and is in the ZIP. Its row says the quality, the pixel size and anything unusual (a format change, fewer pixels, a raised quality). | Nothing. Check the figures if the photo matters. |
| under-floor | The file was smaller than the Leave alone floor (250 KB on most pages), so it was not opened. The original is copied into the ZIP as it is. | Set the floor to Off in the Recipe panel if you want every file processed. |
| grew | The re-encode came out the same size or larger, so it was thrown away and the original went into the ZIP instead. Usual for photos already compressed once. | Nothing: this is the rule protecting the file. Switch off 'anything that came out bigger' only to see the larger copy. |
| over-target | A target or range could not be reached: even at the quality floor and the smallest pixel size tried, the file is still over. The closest result is kept and marked. | Lower the quality floor, crop the photo, or allow a larger size. Nothing is dropped silently. |
| under-min | A range's minimum could not be reached honestly: quality 95 (and, where allowed, more pixels) still came out under it. Nothing was padded. | Use a higher-resolution scan, allow enlarging under Colour and density, or check whether the form accepts it. |
| unsupported-codec | This browser cannot decode the file (HEIC outside Safari, for example) or cannot write the chosen format (WebP in Safari). The original is left alone. | Choose another output format, or open the page in a browser that handles the format. |
| too-many-pixels | The picture is larger than this browser can safely decode in one go. It is left alone rather than crash the tab. | Reduce it in a desktop editor first, or try a desktop browser with more memory. |
| cmyk | A CMYK JPEG from a print workflow. Re-encoding it through a canvas would change its colours, so it is left exactly as it is. | Convert it to RGB in the software that made it if it needs to be smaller. |
| not-an-image | The file's first bytes are not a picture this site reads, whatever its name says. | Nothing; it is counted and left out of the ZIP. |
| error | Something failed for this file alone (the encoder refused it, or a lossless rewrite did not decode to the same pixels). The run carried on. | Retry the failed files from the Export panel; if it fails again, the file is unusual and is safest left as it is. |
| cancelled | The run was stopped before this file started. | Run again; finished files are kept. |
Form checks
With a form preset, each output also gets a line such as “PASS · 38.2 KB (20–50 KB) · 200 × 230 · JPEG · 200 DPI”. It lists every number the preset states and says which one failed. Sizes are rounded down, so a file can never read as inside a limit it is outside. Try it on compress photo for exam form.
Why skips are good news
A compressor that never skipped would be writing larger, worse copies of files that were already efficient and counting them as savings. The skip codes are how this site keeps the total honest; the longer explanation is in files that get bigger. For targets that could not be met, reduce photo size in KB shows the search on one photo.