UnderKB is a browser-only toolkit at underkb.online for people who have a hard kilobyte cap and a file that will not fit. No accounts. No watermarks. Nothing is uploaded. Contact: admin@underkb.online.
Image-only exact-size tools skip PDFs, skip passport centimetres, skip signature PNGs, and skip the 10 KB / 20 KB / 300 KB caps Indian exams and e-Visa actually use. That is the gap this site fills.
Processing uses the Canvas API and PDF.js in a worker with scripting disabled. Close the tab and the files are gone. Pages are pre-rendered for search engines; the compressor still runs only on your device.