# Why Preview’s “Reduce File Size” makes some PDFs bigger or blurry

> Preview’s Reduce File Size filter can make a PDF bigger or blurry. Why it happens, and how to compress a PDF on a Mac with a choice of quality.

Source: https://whizra.com/guides/why-preview-makes-pdf-bigger

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# Why Preview makes a PDF bigger

Preview’s “Reduce File Size” filter uses one fixed setting for every PDF, and it doesn’t check that the result is smaller. So a PDF whose pictures were already compressed can come out bigger, and one with detailed photos comes out blurry.

## What the filter does

File → Export → Quartz Filter → Reduce File Size saves a new copy of the PDF with its pictures made smaller and saved again. The filter has no options in Preview: the same setting is used for a scanned contract, a photo brochure and a text-only report, and Preview saves whatever comes out.

## What you can do instead
- **Keep the original** and compare: if the copy is bigger or blurry, don’t use it.
- **Make your own filter** with a different setting in ColorSync Utility (in Applications → Utilities); Preview lists it under Quartz Filter.
- **Whizra**: select the PDF and type compress it. You pick strong, good or light (or say for email), text stays selectable, and if the result isn’t at least 5% smaller it says so and keeps nothing.

## Questions

**Why is my PDF blurry after Reduce File Size?**

The filter makes every picture smaller with one fixed setting, whatever the PDF is. Detailed photos lose sharpness.

**Why is my PDF bigger after Reduce File Size?**

Preview doesn’t check that the new file is smaller. A PDF whose pictures were already compressed can come out bigger.

**Is there a free way with better control?**

Yes: make your own Quartz filter in ColorSync Utility, or compare a few settings. Whizra gives three qualities and never keeps a result that isn’t smaller.

Checked: 3 Nov 2026.

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Related: [Compress a PDF without uploading](https://whizra.com/guides/compress-pdf-without-uploading) · [Preview vs Whizra](https://whizra.com/alternatives/preview)