Tool facts
- Input and output
- application/pdf → application/pdf
- Files per operation
- 1
- Total input limit
- 100 MiB
- Page limit
- 100
- Processing
- In your browser; no file upload
- Account
- Not required
- Price
- Free
Scope of these facts
- Selected file contents stay in the browser for processing. Loading the website and its separate usage analytics can still use the network.
- Verification covers the declared checks for supported files, not independent certification or acceptance by another portal. A format-signature check is not digital-signature validation.
- JavaScript, the required browser APIs and sufficient device memory are needed. Limits are admission ceilings, not a guarantee for every file, browser or iPhone.
- Lossless refers to supported structural optimization without intentional image-quality reduction, not byte-identical files or guaranteed metadata removal. No target size or reduction ratio is guaranteed.
How it works
- Select one PDF or drop it in the file area.
- Choose Compress PDF to optimize its structure locally.
- Compare original size, new size and percentage reduction. Download the verified smaller PDF.
Lossless structure compression
This first version reduces structural overhead using compressed PDF object tables. It does not rasterize pages, resize images or lower JPEG quality. Every page is reparsed and compared after compression, including its content, resources, page boxes and rotation.
Why some PDFs shrink more than others
Files with uncompressed object tables may become smaller. PDFs already using compact storage, or files whose size comes mostly from images, may see little improvement. If no smaller verified file is produced, the tool tells you. It does not promise an exact target size.
Supported files and limits
Select one supported PDF 1.0–1.7 within the current size and page limits shown in the technical facts above. The bounded parser supports classic cross-reference tables as well as verified object/xref streams, including safely resolved indirect stream lengths and common FlateDecode PNG-predictor xref streams. Signed and encrypted PDFs remain declined, as do unsupported forms, annotations, bookmarks, tagged-document structures and other features that cannot be preserved and verified safely.
Privacy and original files
All processing happens in your browser. Your PDF is never uploaded, logged or stored on our servers. Your original is unchanged. The new file is offered only after it is smaller and passes every required check.
Frequently asked questions
Does compression lower image quality?
This tool currently uses lossless structure compression. It leaves encoded image content and page dimensions unchanged. Image-quality modes are not offered in this version.
Can you compress my PDF to exactly 5 MB?
No. The result depends on the source file. We report the actual local size reduction and do not promise a specific maximum size.
Are PDFs with compressed object or xref streams supported?
Yes when their structural streams fit the bounded safety model. Common FlateDecode object/xref streams, indirect stream-length references that resolve safely, and common PNG-predictor xref streams are admitted before parsing. Unsupported filters, malformed references and resource-limit violations still fail closed.
Can I combine PDFs first?
ZAMAZY Merge PDF is a separate tool for combining supported documents. This page only compresses one PDF.