How is this different from other online PDF tools?

Most online PDF tools send your files to a remote server for processing. This tool processes everything locally in your browser using client-side JavaScript. Your files are never transmitted to any server, which means your document content stays entirely under your control.

Are my PDF files uploaded?

No. Your files are read directly by your browser. Your files are never transmitted over the network. The tool works entirely within the browser tab you have open.

Can I verify that files are not uploaded?

Yes. Open your browser's developer tools (F12), go to the Network tab, and watch for any outgoing requests while using the tool. You will see no file data leave your browser. The site may record an anonymous page-view count, which never includes your files and can be disabled.

Does this tool work offline?

Yes, once the page has loaded the tool processes your files entirely in your browser; tool functionality needs no network connection. You can disconnect from the internet and continue using it.

What happens when I refresh the page?

Because nothing is stored on a server, refreshing the page clears your current session. Any files you had selected will need to be selected again.

Does this tool store my files?

No. Files are held in browser memory only for as long as the page is open. Closing or refreshing the page discards them. Nothing is written to disk by the tool, and nothing is sent to a server.

Can this tool unlock password-protected PDFs?

No. This tool does not attempt to remove or bypass PDF password protection. If you know the password, the Unlock PDF tool on this site can remove it locally; then this tool can process the file.

What technologies does this tool use?

This tool uses pdf.js (Mozilla's client-side PDF engine) in a Web Worker to render pages to canvas, then re-encodes those images with pdf-lib into a new PDF — entirely within your browser.

Does this tool use WebAssembly?

No. pdf.js is a plain JavaScript library — it does not use WebAssembly. All PDF rendering happens in client-side JavaScript within your browser.

How do I compress a PDF with this tool?

Pick a PDF from your device with the file picker, choose a quality level (Low, Medium, or High) from the dropdown, then select Compress. The work runs locally in your browser, and once it finishes you can save the smaller file and see a before/after size comparison.

Why did my file barely shrink, or even get larger?

This tool reduces size by rasterizing each page and re-encoding it as a JPEG, so it mainly helps image-heavy or scanned PDFs. A text-only PDF has little image data to compress, and re-encoding clean vector text as a JPEG can actually make the file bigger rather than smaller.

What do the Low, Medium, and High quality settings change?

Each preset sets both the JPEG quality and the render scale: Low uses the lowest quality at full size for the smallest result, Medium balances quality and size, and High keeps the most detail with the largest output. Because pages are turned into images, the original selectable text and features like form fields, links, and bookmarks are not kept in the result.

Does the Compress PDF tool cost anything to use?

Compress PDF is completely free — no account, no sign-up, and no cap on how many files you reduce, and it always will be. Your PDF never leaves your device: the tool re-encodes each page image directly inside your browser, so your file is never sent to a server. You can confirm this yourself by watching the Network tab in your browser's developer tools while compressing — no file data leaves your device.

Compress PDF Files Privately — Reducing File Size in Your Browser

Select a PDF, choose a quality level, and download a smaller file — page images are re-encoded locally in your browser with no upload.

Quick answer

What it does: Select a PDF, choose a quality level, and download a smaller file — page images are re-encoded locally in your browser with no upload.
Free?: Yes — 100% free, no account or sign-up.
Files uploaded?: No — everything is processed in your browser.
Works offline?: Yes — once the page has loaded.
Best for: Shrinking a scanned or image-heavy PDF to fit a 5 MB or 10 MB email or upload-form limit.
Good to know: This compression approach is lossy — it rasterizes each page and re-encodes it as a JPEG, which reduces visual quality at lower settings.

How it works

Select a PDF file from your device using the file picker.
The file is read into browser memory — no data leaves your browser.
pdf.js renders each page to a canvas in a Web Worker at the chosen quality scale.
Each rendered canvas is re-encoded as a JPEG at the selected quality level, reducing the size of image-heavy content.
pdf-lib assembles the re-encoded pages into a new PDF, which is offered as a download.

When to use this tool

Shrinking a scanned or image-heavy PDF to fit a 5 MB or 10 MB email or upload-form limit.
Reducing the file size of a photo-filled brochure PDF before attaching it to a web form.
Making a large scanned document easier to store and share on a messaging app.
Note: pages are rasterised to JPEG, so selectable text, form fields, hyperlinks, and bookmarks are not preserved. Text-only PDFs see little size reduction.

Frequently asked questions

How is this different from other online PDF tools?: Most online PDF tools send your files to a remote server for processing. This tool processes everything locally in your browser using client-side JavaScript. Your files are never transmitted to any server, which means your document content stays entirely under your control.
Are my PDF files uploaded?: No. Your files are read directly by your browser. Your files are never transmitted over the network. The tool works entirely within the browser tab you have open.
Can I verify that files are not uploaded?: Yes. Open your browser's developer tools (F12), go to the Network tab, and watch for any outgoing requests while using the tool. You will see no file data leave your browser. The site may record an anonymous page-view count, which never includes your files and can be disabled.
Does this tool work offline?: Yes, once the page has loaded the tool processes your files entirely in your browser; tool functionality needs no network connection. You can disconnect from the internet and continue using it.
What happens when I refresh the page?: Because nothing is stored on a server, refreshing the page clears your current session. Any files you had selected will need to be selected again.
Does this tool store my files?: No. Files are held in browser memory only for as long as the page is open. Closing or refreshing the page discards them. Nothing is written to disk by the tool, and nothing is sent to a server.
Can this tool unlock password-protected PDFs?: No. This tool does not attempt to remove or bypass PDF password protection. If you know the password, the Unlock PDF tool on this site can remove it locally; then this tool can process the file.
What technologies does this tool use?: This tool uses pdf.js (Mozilla's client-side PDF engine) in a Web Worker to render pages to canvas, then re-encodes those images with pdf-lib into a new PDF — entirely within your browser.
Does this tool use WebAssembly?: No. pdf.js is a plain JavaScript library — it does not use WebAssembly. All PDF rendering happens in client-side JavaScript within your browser.
How do I compress a PDF with this tool?: Pick a PDF from your device with the file picker, choose a quality level (Low, Medium, or High) from the dropdown, then select Compress. The work runs locally in your browser, and once it finishes you can save the smaller file and see a before/after size comparison.
Why did my file barely shrink, or even get larger?: This tool reduces size by rasterizing each page and re-encoding it as a JPEG, so it mainly helps image-heavy or scanned PDFs. A text-only PDF has little image data to compress, and re-encoding clean vector text as a JPEG can actually make the file bigger rather than smaller.
What do the Low, Medium, and High quality settings change?: Each preset sets both the JPEG quality and the render scale: Low uses the lowest quality at full size for the smallest result, Medium balances quality and size, and High keeps the most detail with the largest output. Because pages are turned into images, the original selectable text and features like form fields, links, and bookmarks are not kept in the result.
Does the Compress PDF tool cost anything to use?: Compress PDF is completely free — no account, no sign-up, and no cap on how many files you reduce, and it always will be. Your PDF never leaves your device: the tool re-encodes each page image directly inside your browser, so your file is never sent to a server. You can confirm this yourself by watching the Network tab in your browser's developer tools while compressing — no file data leaves your device.