Nothing is uploaded. When you drop or pick a PDF, the tool reads it locally with the browser’s File API, renders its pages in memory with the pdf.js engine (whose worker is bundled locally, not fetched from a CDN) and rebuilds the compressed file with the pdf-lib library on your own machine. There is no server, upload, database, API or tracking in the processing path, so certificates, ID scans, mark sheets and private paperwork you are shrinking for a form stay on your device; the tool works offline once cached, and closing the tab discards everything. The only optional network use anywhere on the site is consent-gated advertising, which never sees your files.

It depends on what is inside the PDF. The real savings come from re-encoding images, so a text-only or lightly formatted document usually falls well under 100 KB, often with room to spare. A multi-page scan or a file full of photographs has a floor: past a certain point the pages would turn to mush, so the tool stops at the smallest readable size it can reach and reports that figure with a note rather than producing an unusable file. If you are stuck above 100 KB, enabling grayscale, removing pages you do not need, or splitting the document first will usually get you under the cap. The three variants let you take the Smallest one when you need every byte, or Best Quality when 100 KB is comfortably met.

To reach a target as small as 100 KB the tool leans on lossy compression — it down-samples the page images to a lower DPI and re-encodes them as JPEG, which is how a large file becomes tiny. That trades some sharpness for size, so three variants are generated in one pass (Best Quality, Balanced and Smallest) and the tool defaults to the best one that still fits. One honest note: when whole pages are rasterised to hit 100 KB, the text on those pages becomes part of the image and is no longer selectable or searchable; if you need the text to stay selectable, a 100 KB target may be too aggressive for that document and a larger size would keep it live. For most single-page scans and certificates headed to an upload form, the 100 KB result stays perfectly legible.

Many online forms — especially government recruitment and examination portals — cap each uploaded document, photo or signature at 100 KB to keep their databases manageable and processing uniform, and every year a large number of applications are rejected for oversized files. When your certificate, mark sheet or signed form is a few hundred kilobytes, you need it under 100 KB to complete the submission. This tool is built for exactly that: the target is fixed at 100 KB so you can drop the PDF and download a version that clears the cap, without hunting through compression settings. If the portal wants an even smaller cap, a sibling tool targets 50 KB, and larger presets (150 KB, 200 KB and up) exist for looser limits.