PDF compression test
In short: on our test files, the Compress PDF tool reduced a 10-page scan from 16.9 MB to 710 KB (−96 %) and an 8-page report full of images from 34 MB to 618 KB (−98 %) with the default “Automatic” setting. A text-only PDF went from 40 KB to 28 KB (−29 %) with the text kept selectable. Everything ran in the browser, without uploading the files.
Results
| Test file | Automatic (default) | Lossless | Light, as image | Medium, as image | Strong, as image |
|---|---|---|---|---|---|
| Text report 20 pages, 40 KB | 28 KB (−29 %) text kept | 28 KB (−29 %) text kept | Already optimised: original kept (40 KB) | ||
| Scanned document 10 pages, 300 dpi, 16.9 MB | 710 KB (−96 %) pages as images | Already optimised: original kept | 1.4 MB (−92 %) | 710 KB (−96 %) | 282 KB (−98 %) |
| Report with images 8 pages, large lossless images, 34 MB | 618 KB (−98 %) pages as images | 26.1 MB (−23 %) text kept | 1.2 MB (−97 %) | 618 KB (−98 %) | 273 KB (−99 %) |
Processing time with the Automatic setting: 0.7 s for the text report, 5 s for the scan, 25 s for the report with images.
What the results show
- Scans and image-heavy PDFs shrink the most: −92 % to −99 %, enough to send a 17 MB scan by email or to an online form limited to 1 or 2 MB.
- Text PDFs are already light: the lossless optimisation still saves about 30 % and keeps the text selectable. The tool never makes a file bigger: if it cannot do better, it keeps the original.
- “Automatic” picks the method for you: it first tries a lossless optimisation, and only saves the pages as images when the gain is much bigger. The result always tells you which method was used.
- “Lossless” is the choice when the text must stay selectable (to copy it or search it), even if the file stays bigger.
Test method
- Files, created for the test: a 20-page text report (standard fonts); a 10-page A4 document scanned at 300 dpi (JPEG, high quality); an 8-page report with one large lossless (PNG) illustration per page and text.
- Tool: LUNYCE Compress PDF, all five settings, in the Chromium browser on a Linux computer, October 2026.
- Measures: file size before and after, as shown by the tool. Times depend on your device and will vary.
Your results will depend on your files: a PDF that is already compressed shrinks less. Try with your own file: it is free and it is never uploaded.
See also: Compress an image · Reduce a photo to a size in KB · PDF tools that don't upload your files.