Compress PDF
NewReduce PDF file size instantly in your browser — free, private, and entirely client-side. Choose high, medium, or low compression. No uploads, no sign-up required.
The Compress PDF tool reduces PDF file size entirely in your browser using pdf-lib. No server upload, no account required, and nothing stored anywhere.
Choose from three compression levels: High (smallest file, standard quality), Medium (balanced size and quality), or Low (largest file, best quality). Estimated output sizes are shown before you compress.
Your files are never transmitted anywhere. All processing happens locally in your browser using a trusted open-source library.
- 1Upload your PDF file by dragging it into the upload area or clicking Browse File.
- 2Choose a compression level — High, Medium, or Low — based on your quality needs.
- 3Click Compress PDF to process the file in your browser.
- 4Download the compressed file when it appears in the result panel.
No. All processing happens entirely in your browser using pdf-lib. Your files never leave your device — they are never uploaded to any server, and no one else can access them.
Only PDF files (application/pdf) are supported. Files with any other MIME type will be rejected immediately with an inline error message before any processing begins.
High compression produces the smallest output file by enabling object stream compression — ideal when file size matters most and a slight reduction in quality is acceptable. Medium compression (the default) balances file size and quality, also using object stream compression with a more conservative size estimate. Low compression preserves the original document structure without stream compression, resulting in the largest output but the best possible quality.
No. Password-protected or encrypted PDFs cannot be compressed because the tool cannot access their contents. If you attempt to compress such a file, the tool will display an inline error and ask you to try a different file.
The output filename is derived from your original filename with "-compressed" inserted before the .pdf extension. For example, "report.pdf" becomes "report-compressed.pdf". The suffix is always lowercase regardless of the original extension casing.
Your PDF is held in your browser's memory only for the duration of the session. No data is written to localStorage, sessionStorage, IndexedDB, or any other browser storage. When you click "Compress Another", navigate away, or close the tab, all in-memory references are cleared and no data is recoverable.
The tool works in all modern browsers — Chrome, Firefox, Edge, and Safari. JavaScript must be enabled. Internet Explorer is not supported.
Yes. The tool accepts PDF files up to 50 MB. Files larger than 50 MB are rejected with an inline error before any processing begins.
It can. High and Medium compression use object stream compression which may reduce the visual quality of images embedded in the PDF, especially at High level. Low compression preserves the original document structure and produces the closest result to the original quality.
PDF compression via pdf-lib works by restructuring the document and applying object stream compression. If your original PDF was already well-optimised, generated by a tool that uses tight compression, or contains content that does not compress well (such as already-compressed images or encrypted streams), the re-written document may end up equal to or slightly larger than the input.