How much can I reduce the file size?

It depends on how the file was written, and there is no setting that changes it. A text-heavy PDF saved without object streams can shrink by a third or more, while a file that already uses object streams, or a scanned PDF, often changes by only a few percent. Preview Compressed Size shows the exact figure for your file.

Does compressing lose any quality?

No. The compression is lossless: nothing is resampled, re-encoded or downsampled, so text stays sharp and pages render exactly as before. That is also why the savings on image-heavy files are modest.

Can I compress a PDF for email attachment?

Sometimes. If the reduction brings the file under your mail provider limit, download it and attach the copy. If a scanned or photo-heavy file stays too large, this tool cannot shrink the images, so remove pages you do not need or rescan at a lower resolution.

How does the compression work?

It rebuilds the file from its pages and writes it with object streams, which pack the many small objects that describe a PDF into compressed blocks. Objects that no page references are left out. The page content itself is not touched.

Why did compressing my PDF document barely change its size?

Because most of its size is data this tool does not re-encode. In a scanned PDF almost every byte is image data, and images are copied as they are. A PDF that was already written with object streams has little structural overhead left to remove, so the result can be within a percent of the original.

Which PDFs compress well?

Text-heavy documents with many pages and many small objects, especially ones written by older software without object streams: reports, generated invoices, exports from word processors and drawing tools. Those carry a lot of structural overhead, and that is exactly what this removes.

Why is there no Low, Medium or High compression setting?

Because they would all produce the same file. Without re-encoding images there is only one way to repack a PDF, so the tool offers that one and shows you the measured result instead of a set of buttons that change nothing.

Why is my file bigger after compressing?

It can happen with a file that was already written with object streams and aggressive structural packing: rewriting it gains nothing and the new cross-reference table may cost a few bytes. The results box then says the PDF is already well-optimized. Keep the original in that case.

Does compressing multiple PDF files at once work the same way?

No, the tool compresses one PDF at a time. The file picker takes a single PDF, and if you drop several files only the first is loaded. Repeat the steps for each file; the result for each depends on how that file was written.

Do bookmarks survive compression?

No. The file is rebuilt as a new document from copied pages, and the outline tree is not carried across.

Do links still work after compressing?

Links to websites do, because they are page-level annotations copied with their pages. Links that jump to another page inside the document stop working, because they point at a copy of the target page that is not part of the rebuilt file.

What happens to form fields?

They stop being fillable, because the document-level form dictionary is not copied into the rebuilt file.

Can I compress a password-protected PDF?

No. Encrypted files fail to load and the tool shows Error loading PDF. Please try another file. Remove the protection first.

Why does the tool not estimate the size before I preview?

Because an estimate based on file size alone would be a guess. The saving depends on how the PDF was written, so the only number shown is the Compressed figure from Preview Compressed Size, which is the measured size of the file you would download.

Is document metadata preserved?

No. Title, author and keywords are not carried into the rebuilt document.

Are my files uploaded?

No. Compression runs in your browser and the PDF never leaves your device, which makes it safe for confidential documents.

Does it work offline?

Yes. Once the page has loaded no network connection is needed.

Is my original file changed?

No. A new document is offered as a download and the original stays on your disk untouched, which matters here because you may want to keep it if the saving is small.

Compress PDF

Reduce PDF file size by repacking the document structure, without re-encoding text or images

Compress PDF

Click to upload PDF

Category:pdf

Mode:Offline

Version:1.0.0

Access:Free

What is Compress PDF?

Compress PDF interface on Toolz.dev - Reduce PDF file size by repacking the document structure, without re-encoding text or images

Compress PDF is a free online tool that reduces the file size of your PDF documents without touching their quality. Large PDFs are difficult to share via email, slow to download, and consume unnecessary storage space. This tool rewrites the file in a tighter form so it takes less space where the structure allows it.

There is no compression level to choose, because the tool has only one way to repack a file and a Low, Medium or High button would all give the same result. There is no guessed saving either. The size next to the original reads Not measured yet until you click Preview Compressed Size, which runs the compression and shows the real result before you download.

All compression happens entirely in your browser. Your PDF files are never uploaded to any server, making this the safest option for compressing confidential documents. Simply upload, preview the real size, and download the optimized file.

A worked example shows what file compress PDF tools of this kind can and cannot do. A 12-page, text-only PDF written without object streams loads as 6.25 KB. The panel shows Not measured yet until Preview Compressed Size replaces it with 3.41 KB, and the results box reports a Size reduction of 45.5%. Save the same pages with object streams (3.44 KB) and the result is still 3.41 KB, a saving under 1%, which is why compressing PDF document size is worth checking before you rely on it.

It is worth being honest about how much this can save, because it depends entirely on what is inside your file. The tool repacks the document structure and drops objects nothing references, which is where the reduction comes from. It does not re-encode images. A text-heavy report with a lot of internal overhead can shrink noticeably; a scanned document that is essentially a stack of photographs will barely move, because the photographs are re-embedded exactly as they were. If your file is large because it is scanned, the real saving is in removing pages you do not need rather than in compression. Nothing is resampled or degraded, so text stays sharp and images keep their resolution. If a file will not load, it is likely password-protected and needs unlocking first.

How to use Compress PDF?

Upload your PDF

Drag and drop a PDF file or click to browse and select one from your device. The tool displays the original file size.

Check the original size

The panel shows the original size next to Not measured yet. There are no settings to change, because every file is repacked the same way.

Preview the real size

Click Preview Compressed Size. Not measured yet is replaced by the Compressed size, and the results box shows the original size, the compressed size and the reduction.

Download the compressed PDF

Click Download Compressed PDF to save a copy named after the original with _compressed added. If the reduction is zero or negative, keep the original instead.

Key Features

Lossless by Construction

The document is repacked and unreferenced objects are dropped; images are never re-encoded, so nothing in the file is degraded

Real Size Preview

Preview Compressed Size runs the compression without downloading, so you see the actual result before saving anything

Size Comparison

See the original and compressed file sizes side by side, with the percentage reduction when there is one

Honest About Optimized Files

When a PDF does not get smaller, the result box says the file is already well-optimized instead of inventing a saving

Frequently Asked Questions

Yes. Compress PDF is free, no signup, and adds no watermark. It runs in your browser, so there is no upload size cap; the practical limit is your device memory.