Will the quality of PDF displays change after compression?

This tool is compressed mainly through structural optimization and metadata cleansing, without compromising the re-sampling of page contents (including pictures, text) and with largely constant visual quality. Use professional desktop software if deep graphic compression is required.

PDF compression tool - free online compression of PDF files, reducing volume-neutral mass in KiloCell

Q: Why is the compressed file bigger than the original one?

Some PDFs have been highly optimized or are very concise in their structure, and may be slightly expensive to write back into the object stream, leading to flat or slightly increased volume. This is normal and can be either graded or optimized.

Q: Support password-protected PDFs?

Tools will try to read encrypted PDF; If strict editorial restrictions are opened, they may not be handled. It is suggested that password protection be removed and compression reduced.

Q: Support lot compression of multiple PDFs?

The current version supports single file processing. If batch compression is required, upload the files in order of processing and download them separately.

Upload PDF files

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Click or drag to upload PDF files

PDF compression user instructions

Select the compression level after uploading PDF, and the tool will be downloaded after processing the browser to optimize the document structure locally and to clean redundant metadata. Can not append message to mh folder: %s: %s

Other ways to reduce PDF size

In addition to using this tool, the following methods can be effective in reducing the PDF volume:

Select the option "minimum file size" when Word/WPS saves as PDF
Optimizing PDF with Adobe Acrobat Pro to compress embedded images
For a scanning PDF with a large number of pictures, you can compress the picture and reprint it to PDF.
Remove unnecessary layers, notes and attachments in the document

❓ Common question answer

Q: Will the quality of PDF displays deteriorate after compression?

A: This tool is compressed mainly through structural optimization and metadata cleansing, without compromising the content of the page (including pictures, text) and with essentially the same visual quality.

Q: Why is the compressed file bigger than the original one?

A: Part of the PDF file has been highly optimized or is very simple in its own structure, and at this point recompression may result in a slight increase in the document as a result of the rewriting of the cost. It's normal.

Q: Support password-protected PDFs?

A: The tool will try to read encrypted PDF and may not be able to handle it if the editing limit is opened. It is suggested that password protection be removed before compression.

Q: Support bulk compression of multiple PDFs?

A: Current version supports single file processing. If batch compression is required, upload the files in order of processing and download them separately.

Guide to the full use of PDF compression tools

This page is used to reduce PDF size in browser: by drag-and-drop #uploadZone or File Selection #fileInput Loading documents (no more than 100 MB recommended) with scripts reading pages and displaying file names and sizes in pdf.js; Select compression level (high quality) high / Balance medium Default / Minimum Volume low) Click "Start compression" to call compressPDF()。 Processing pdf-lib-based rewrite documents locally: balancing with the smallest sizes clears metadata such as headings, authors, themes, etc.; Open object stream while saving useObjectStreams to optimize the structure. Result area displays original size, compression size, savings ratio, downloadable *_compressed.pdf。 Documents are not available on the server and are suitable for thinness and pre-archiving of mail attachments; Not the Adobe Acrobat scale photo replicators compressor.

What's the third set of compressions for?

High quality: Keep metadata as much as possible, have a lighter structure, are suitable for print/archiving scenes that still require document properties, and volume decreases are usually limited.
Balance (recommended): Clean up metadata and optimize the flow of objects, and reduce the volume to compatibility, with priority being given to daily distribution.
Minimum volumeMore radical (with further flattening options) in balancing strategies, more suitable for the ceiling of the attachment to the mailbox when it is tight.
The interface "about 10-20% / 30-30% 50% / 50-70%" is an experience zone, depending on whether the original document is compressed or contains a large number of pictures.
The PDF, which is highly optimized or has a very simple structure, may have a flat or even slight increase in volume after compression, with a potential 0 per cent savings in the result area.

Recommended Operational Steps

Drag PDF into upload area or click on the selected file; The number and size of confirmations are normal.
Selecting levels by purpose: high quality in printing, daily balance in print, minimum volume in mail.
Click "start compression" to observe progress bars; When completed, three sets of statistics were compared.
Download a compressed file, open the page with the reader to check the front page and the key page, confirming that the text is normal with the layout.
If not satisfied, remove the point and retry it in one set; Use desktop software for more robust graphic compression.

Capacity boundary (read first)

The main reason is to use metadata cleaning and document structure/object flow optimization, without damaging re-sampling of embedded images.
Scan, high-level atlas, PDF size is large in pictures and the reduction in this tool may not be significant.
Encryption or strict permissions for PDF may not work, please declassify and process (load with ignoreEncryption).
Currently only single documents; Batch by volume. Super-large files are restricted by browser memory, possibly in Cardon or failed.
The file data in the memory after closing the tab will be released, and please download the results in time.

Supplement to frequently asked questions

Will the mass change when it's compressed?

Text and pictures are not generally retraced to the detriment of sampling and should be viewed in a manner that is close to the original text. If you need to reduce the scan significantly, use tools to support image downsampling (e.g. Acrobat Optimize PDF), rather than relying only on this page.

Why is the volume almost unchanged or even larger?

Rewriting PDF containers may introduce a small cost when the original document is clean. You can select another level or process it from the source (Word export the "minimum file size", first pressure map and then create PDF).

Is privacy safe?

Compression is done locally and not uploaded through the site server. Public computers are required to download the results and close the page so that sensitive contracts are not left in the browser download records for long periods.

Related tools

After volume processing, you can use other PDF/ media capabilities in a string of stations as required:

📄 PDFMinifytools