Loona Compress PDF Online - Free
Upload portals and email often reject big PDFs. Compress yours here and see the true before and after size. Standard mode is lossless for text documents; Strong mode squeezes scanned and photo-heavy PDFs much further by converting pages to images - the result is clearly labelled, never hidden.
How to compress a PDF
- Choose the PDF you want to shrink - its current size appears right away.
- Pick Standard for text documents (keeps text selectable) or Strong for scans and photos, then choose a quality level.
- Click "Compress PDF", compare the honest before and after sizes, and download.
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Frequently Asked Questions
What is the difference between Standard and Strong mode?
Standard re-saves the PDF with object-stream compression - text stays selectable and quality is untouched. Strong renders each page as a compressed JPEG image, which shrinks scans dramatically but makes pages image-based.
Why did my file not get smaller in Standard mode?
Some PDFs are already well compressed, so re-saving changes little. Try Strong mode for scanned or photo-heavy files.
Are compressed files uploaded to a server?
No. Both modes run 100% in your browser; your document never leaves your device.
Which level should I choose in Strong mode?
High keeps pages sharp for printing, Balanced suits most sharing, and Small gives the tiniest file for strict upload limits.
How it works
Everything runs locally in your browser - your file is never uploaded. In Standard mode the document is loaded with pdf-lib and simply re-saved with object streams switched on, which packs the PDF's internal parts into compressed streams. No page content is touched: text stays selectable and images keep their exact quality, so this mode is completely lossless. In Strong mode the browser renders every page onto a canvas with PDF.js at the scale you pick (High 2x, Balanced 1.5x, Smallest 1x) and saves each rendered page as a JPEG (92%, 80% or 65% quality) on a same-sized page in a new PDF - the pages become pictures, which is why scanned documents shrink so much.
Worked example
A signed, scanned contract comes to 18 MB over 24 pages, but the upload portal accepts at most 10 MB. Standard mode re-saves it losslessly at almost the same size, because scans are already mostly image data. Strong mode at Balanced rebuilds every page as a 1.5x JPEG and the file drops to a small fraction of the original - comfortably under the limit - with pages that still read clearly, though the text is now part of the images.
Frequently asked questions
Will text stay searchable after Strong mode?
No. Strong mode turns each page into a JPEG image, so text can no longer be selected, copied or searched. Use Standard mode whenever keeping live text matters.
Does Standard mode reduce the quality of my images?
No. Standard mode only re-packs the file's internal structure with object streams - every image and every character is stored exactly as before, so quality loss is impossible in this mode.
Can the compressed file come out larger than the original?
It can, for a PDF that is already heavily optimised. The tool reports this honestly after processing - the status line tells you the file came out larger and that the PDF was already compact, so you can simply keep your original.
What happens to forms and clickable links in Strong mode?
They are flattened into the page picture. The new document looks the same, but form fields can no longer be filled in and links are no longer clickable. Standard mode leaves interactive elements working.
Is there a maximum file size?
There is no limit set by us - the practical limit is your device's memory. Strong mode handles one page at a time, and the progress bar shows how far it has got, which keeps even long documents manageable.
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