PDF Compressor
Compress a PDF in your browser using two strategies — structural re-save and page rasterisation. Picks the smaller result automatically. No upload required.
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PDF Compressor reduces the file size of a PDF entirely in your browser — no file is ever uploaded to a server. It automatically tries two compression strategies and keeps whichever one produces the smaller result.
How it works
When you click Compress PDF, the tool runs two passes in parallel:
Structural re-save — pdf-lib re-encodes the existing PDF using object streams and flate compression. This is fast and lossless. It works well on PDFs that were saved without compression, or that contain redundant cross-reference data. Vector graphics and selectable text are fully preserved.
Rasterisation — PDF.js renders each page onto a canvas at 144 DPI, then each frame is encoded as a JPEG and reassembled into a new PDF by pdf-lib. This works well for PDFs with large embedded photographs or uncompressed scanned images.
The smaller of the two outputs is offered for download. If neither result beats the original file size, the tool tells you the PDF is already well-optimised and no download is presented.
Reading the result
After compression completes, a card shows the original size, the compressed size, and the percentage reduction. The savings badge uses a green background to indicate a successful reduction.
What types of PDF compress well?
Scanned documents, design exports, and PDFs with high-resolution embedded images typically compress the most — reductions of 50–90% are common. Short word-processor documents that are already text-only may see little or no reduction, and the tool will tell you so.
FAQ
Does compression preserve selectable text?
It depends on which strategy produces the better result. If the structural re-save wins, text, links, and annotations are fully preserved. If rasterisation wins, each page becomes an image and text is no longer selectable. In both cases the page dimensions and visual appearance remain unchanged.
Is there a file size or page limit?
There is no enforced limit. Very large PDFs — hundreds of pages or files over 100 MB — may be slow to process depending on the browser and available memory. For those cases a desktop tool such as Ghostscript will be more reliable.
Why does the tool sometimes say compression is not possible?
Some PDFs are already well-optimised — for example, a short vector document with no embedded images and already-compressed object streams. In that case both strategies produce a file at least as large as the original, so the tool reports that no reduction was achieved rather than offering a download that would make the file bigger.