Compress PDFs. Smaller, on your device.
Shrink PDF file sizes by up to 70% while keeping text crisp and images clear. All processing happens in your browser.
What is PDF compression?
PDF compression is the process of reducing the file size of a PDF document while keeping its content usable. Depending on what's inside the PDF, different strategies apply. Documents that contain photographs, scanned pages, or illustrations can be compressed significantly by re-encoding their embedded images at a lower quality setting. Documents that are mostly text and vector graphics compress far less, because that content is already stored in a highly efficient format.
Foliopress focuses on image re-compression — the technique that produces the largest file size savings. For each JPEG image embedded in your PDF, the tool decodes it, renders it through a canvas, and re-encodes it at a lower quality level. The surrounding document structure — text, fonts, page dimensions, form fields, hyperlinks — is preserved exactly. Only the images change.
Why compress PDFs in your browser?
Every mainstream PDF compression service on the internet requires you to upload your file to a server. The file travels over a network, gets processed on hardware you don't control, and — even if the service claims to delete it — exists outside your device for some period of time. For personal files, that trade-off may be acceptable. For contracts, medical records, legal documents, or financial statements, it is not.
Foliopress compresses PDFs entirely within your browser. When you drop a file onto the tool, it is read into your browser's local memory using the Web File API. The compression — including image decoding and re-encoding — runs in a JavaScript sandbox in your browser tab. The output is generated in memory and offered as a download via a local object URL that is only valid during your current session. Nothing is transmitted to a server. There are no accounts, no upload queues, and no data retention questions to worry about.
How much can you compress a PDF?
Realistic expectations depend heavily on the content of your specific PDF. Image-heavy files — scanned documents, photo books, brochures, product catalogues, academic papers with figures — can shrink by 40–70% with the recommended setting. A 10 MB scanned document might come down to 3–4 MB. Files that are almost entirely text, such as exported Word documents or generated reports with no photographs, may shrink by only 5–15%, because there are few images to compress.
The "maximum compression" preset achieves the smallest output by encoding images at a lower quality threshold. This is appropriate when file size is more important than pixel-level fidelity — for example, when sharing a document over a messaging platform with attachment limits, or archiving a large collection of scanned receipts. The "less compression" preset keeps image quality high while still achieving modest size reductions, which is suitable for print-ready materials or documents where visual quality must be preserved.
If your compressed PDF is only slightly smaller than the original, the document likely contains very few raster images. In that case, Foliopress will show you an honest summary of what was achieved rather than overstating the result.
How Foliopress keeps your files private
The compression logic is built on pdf-lib, a JavaScript PDF engine that runs entirely in the browser. When you add a file, the browser reads it into an ArrayBuffer using the standard File API — a local memory operation with no network activity. The pdf-lib engine then parses the PDF structure, locates embedded image objects, and processes them using the browser's built-in Canvas API for image re-encoding. The final compressed bytes are written into a Blob URL — a temporary local reference that exists only in your current browser tab.
Foliopress has no server-side processing for this tool. There is no backend that receives your file, no cloud storage, and no analytics on what documents you compress. The only thing that leaves your device is the download itself, which goes to your own disk. For anyone who regularly handles documents with sensitive content, this architecture is not just a convenience — it meaningfully reduces the risk surface compared to any upload-based service.