200KB is the limit that catches most people: it is common on government upload forms, job portals and email attachments. This page compresses a PDF toward that target without sending it anywhere.
Many upload forms cap attachments at 200KB or 250KB per file. Scanned documents are the usual culprit, because a phone photo of a page is often 1-3MB on its own. Text-based PDFs are usually already far smaller.
To reach a small target the compressor has to rasterise pages, which turns selectable text into an image. That is acceptable for a scan you are uploading, but it is a bad idea for a document that must stay searchable or machine-readable.
Split the document into separate files and upload them one at a time, or reduce the scan resolution before compressing. A 300-page scan cannot reach 200KB without becoming unreadable.
No. Compression runs in your browser using the PDF already on your device. You can confirm in DevTools, Network tab, that no file leaves the page.
Strong compression rasterises pages, so text may stop being selectable. If you need searchable text, choose the lightest compression option instead.
Not always. Very long or heavily scanned documents may not get that small without becoming unreadable. The tool reports the real result rather than promising a target.