I built UnderByte because I kept running into awful upload forms that reject files for being a few KB too large, especially for PDFs, passport photos, signatures, resumes, and government forms. Most compressors either upload your files, make you guess the quality settings, or don’t aim for an exact target size. So I wanted something simpler: pick a file, set a limit like 200 KB or 1 MB, and get the smallest acceptable result without sending the file to a server. The whole point is speed, privacy, and less trial-and-error. What makes UnderByte different is the “exact size limit” focus and the local-first approach. It supports JPG, PNG, WebP, and PDF, and batch mode is there for people who need to handle multiple uploads at once. I’d love feedback on the UX, edge cases, and what upload workflows you run into most often.

UnderByte

Compress images and PDFs to exact size limits

Compress images and PDFs to exact size limits