How To Compress A PDF Online
This PDF compression tool is useful for contracts, resumes, reports, scanned documents, invoices, course files, and PDFs that need to meet an upload size limit. You can upload one PDF or many PDFs at once, choose a compression mode, and start batch compression. Each file shows the original size, compressed size, page count, and saved percentage. Results can be downloaded one by one or exported together as a ZIP. All processing runs locally in your browser, without uploading the file to a server.
If you want to preserve selectable text, vector graphics, page structure, and copyable content as much as possible, choose the text-preserving mode. It uses the open-source pdf-lib library to rewrite PDF object streams and optimize the document structure. This mode is fast and safer for text-based PDFs, but it may not significantly reduce PDFs that are already optimized or made mostly of scanned images.
If your PDF mainly contains scanned pages, photos, or image-heavy pages, choose the smaller-file mode. This mode uses PDF.js to render each PDF page in the browser, then writes the rendered pages back into a new PDF as JPG images with pdf-lib. It often reduces image-heavy PDFs more effectively, but the output becomes image-based, so selectable text, links, forms, bookmarks, and some vector information may not be preserved.
Which PDF Compression Mode Should You Use
Start with the text-preserving mode when you are unsure. It is faster, changes the original PDF structure less, and is better for batch processing multiple text-based PDFs. If the file size is still too large, use the smaller-file mode. In smaller-file mode, balanced compression is a good default. Choose smaller file when you mainly need preview or upload compatibility, and choose clearer pages when the PDF needs to stay easier to read or print.
The tool keeps “use the original if compression makes it larger” enabled by default. Browser-based PDF compression cannot guarantee that every PDF becomes smaller. Some PDFs have already been compressed by Acrobat, Ghostscript, office software, or another optimizer. Rewriting or rasterizing them again can sometimes add overhead. Keeping the original avoids making the download larger than the uploaded PDF.
Why Some PDFs Do Not Compress Much
A PDF can contain text, fonts, vector graphics, images, scanned pages, forms, annotations, bookmarks, and metadata. The largest savings usually come from large embedded images, scanned pages, or unoptimized object streams. Text-only PDFs are often already small, and previously optimized PDFs may have little room left for additional compression.
This free online batch PDF compressor is designed for practical daily use: no software installation, no server upload, local browser processing, and a clear result summary. It helps with PDF compression, reducing PDF file size, email attachment limits, upload limits, and quick document sharing.