How to use Compress PDF
- 1
Choose one or more PDFs.
- 2
Pick a level: Light keeps every pixel, Balanced suits most files, Strong squeezes hardest.
- 3
Press Compress PDF and compare the before and after sizes.
Where PDF size comes from
In most heavy PDFs, photos and scans account for nearly all of the bytes. A phone photo dropped into a report may be 4000 pixels wide even though it is printed two inches wide. Text, vector drawings and fonts are usually small by comparison.
What each level does
Light is lossless: it recompresses internal streams and packs objects together, which typically saves a few percent and never changes how anything looks. Balanced also re-encodes large JPEG and uncompressed images at good quality and caps them at about 1800 pixels on the long side — fine for screens and office printing. Strong caps images at about 1100 pixels with stronger JPEG compression; use it when the size limit matters more than zooming in on photos.
When compression cannot help
A PDF that contains only text and vector graphics is often already compact. If the compressed version would be bigger than the original, FileSwiftly tells you and gives back the original instead of a worse file. Images with transparency masks or unusual color spaces are left untouched to avoid color shifts.
Checking the result
The result screen shows the old size, the new size and the percentage saved. Open the downloaded file and zoom into a photo to confirm the quality is acceptable before deleting your original.
Compress PDF: frequently asked questions
Is the compression lossless?
The Light level is. Balanced and Strong re-encode images, which is lossy for photos but keeps text and vector graphics exactly as they were.
How much smaller will my PDF get?
Scanned and photo-heavy PDFs often shrink by 50–90% on Balanced. Text-only PDFs may shrink by only a few percent.
Does compression remove text or links?
No. Text, links, form fields and bookmarks are kept.
Why is the compression done in my browser?
So that confidential documents never leave your computer. The trade-off is that very large files take as long as your device needs to process them.