About the PDF Compressor Online Free Tool

The PDF Compressor Online Free Tool reduces PDF file size using either a fast rewrite path or a raster compression path. It is useful when a PDF is too large for upload, email, support portals, or storage limits and you need a smaller downloadable copy.

Compression runs on the IO Tools server using Ghostscript, with an in-browser fallback when the server pass is unavailable. Uploaded files are processed and deleted immediately; they are never stored or shared. Some already optimized PDFs cannot be reduced further, in which case the original is kept and the output summary says so.

How to Compress PDFs Online

1. Choose a PDF file.
2. Set the compression strength. In simple mode, the slider chooses practical mode, quality, and scale settings.
3. Open more options to override fast rewrite versus raster mode, JPEG quality, render scale, and metadata stripping.
4. Compress the PDF, review the size change and preview, then download the result.

How Compression Runs

This tool first tries a server-side Ghostscript pass. That downsamples and re-encodes the images embedded in the PDF while leaving text and vector artwork as real vector content, so the result stays selectable, searchable, and sharp at any zoom. The strength slider controls the image resolution target, from 300 dpi for a quality-first pass down to 72 dpi for the smallest file.

If the server pass is unavailable, the file is larger than 60 MB, or the PDF is encrypted, the tool falls back to processing entirely in your browser. Browser mode cannot re-encode embedded images, so it achieves far less: the fast rewrite only re-saves the file structure, and raster mode shrinks well only by converting pages to images, which loses selectable text.

Choosing Options Correctly

Strength:
- Lower values keep images near print quality and shrink less.
- Higher values downsample images harder for the smallest file.
- Text stays vector at every setting on the server pass.

Fast rewrite (browser fallback):
Use this for a safer cleanup pass that preserves page content more directly and can strip metadata.

Raster mode (browser fallback):
Use this for scanned or image-heavy PDFs when stronger compression matters more than selectable text or perfect sharpness.

Common Use Cases

• Compressing a PDF before attaching it to email or a ticket.
• Reducing scanned or image-heavy pages with raster compression.
• Stripping metadata when preparing a redistributed copy.

Quick FAQ

What is the difference between fast rewrite and raster mode?
Fast rewrite tries to optimize the PDF structure. Raster mode redraws pages as images, which can reduce size but may soften text.

Can compression make a PDF larger?
Yes. Some PDFs are already optimized, and re-encoding can occasionally increase file size.

Will my original PDF be changed?
No. The compressed result is downloaded as a new file.

Is the PDF uploaded?
Yes, for the main compression pass. Real compression means re-encoding the images inside the PDF, which a browser cannot do, so the file is sent to the IO Tools server, processed with Ghostscript, returned, and deleted immediately. It is never stored, indexed, or shared. Files above 60 MB, and any file the server cannot process, are handled entirely in your browser instead.