A 100KB cap is one of the strictest upload limits you will run into online, usually hardcoded into an older government portal, exam board, or scholarship application form. Compress PDF can get most single-page, text-heavy or lightly scanned documents under that ceiling with the Extreme preset, though a guarantee is not possible for every file.
Compress a PDF nowPortals that enforce a 100KB cap were typically built years ago around narrow server storage and slow connections, and many have never raised the limit even though the constraint no longer makes technical sense. In practice, 100KB only leaves room for a single page of mostly text or a lightly compressed scan — a multi-page document, a high-DPI scan, or a page with a photo will usually need to be split or re-scanned at a lower resolution before it fits, no matter how aggressive the compression.
A 100KB target is realistic mainly for a single page of mostly text or a lightly scanned image — if your file has several pages or was scanned at high resolution, it is unlikely to fit no matter which preset you pick.
If the form only needs one page (like a signature page or ID photo) but your PDF has several, extract just that page before compressing — compressing the whole document will rarely get under 100KB.
Open Compress PDF, add your file, and choose the Extreme quality preset — it prioritizes file size over image fidelity, which is exactly the trade-off a 100KB cap requires.
Compress PDF shows the resulting file size right away, so confirm it is actually under 100KB before uploading it to the portal — if it is still too big, split the document further.
No single setting can guarantee an exact byte count, since the tool works with Low, Recommended, and Extreme quality presets rather than a byte-exact target. A single scanned page usually gets under 100KB at Extreme, but a longer or higher-resolution document might not.
Split the PDF into individual pages and compress only the page the form actually requires; carrying extra pages is usually what pushes a file over 100KB even at the strongest preset.
Many of these upload systems were built during an era of limited server storage and bandwidth and were never revisited once broadband and cloud storage became standard, so the old byte ceiling just stuck around.