Compress PDF
Make a PDF smaller when the file can actually shrink, without sending it to a server.
Processed locally in your browser.
or drop it here
One PDF at a time.
Your smaller PDF is ready
- Original
- Compressed
- Saved
This PDF is already well optimized.
PDFZaro did not find a smaller result worth replacing the original with.
How compression works
PDFZaro reads the file in your browser, tries a structural cleanup, and may recompress images when that is likely to help. Each result is checked before you can download it. If nothing is usefully smaller, you get the original file back.
Compression levels
- Recommended keeps image quality first. It cleans up structure and recompresses images that are not already JPEG.
- Strong aims for a smaller file and will recompress photographs, so some image detail can soften.
- Maximum pushes image compression further. Text that is real text stays text. Pages are not turned into pictures.
What happens to image quality
Structural cleanup does not resample pictures. Image compression does, and it can be visible on photographs, screenshots, and scans. Recommended skips images that are already JPEG so it does not damage them a second time. Strong and Maximum may compress those images again. PDFZaro does not claim that image compression is lossless.
Privacy
Analysis, compression, checks, and the download all happen in this browser. The PDF bytes are not posted to PDFZaro. The page does load its own scripts and the compression engine from this site. That traffic is the program, not your document. The file name is not sent to analytics.
Why some PDFs shrink more than others
A page of text or a drawing is often already compact, so the file barely changes. A high-resolution photograph, a screenshot, or a lossless image usually has more to give. A scan that is one image per page can shrink. A black-and-white scan that is already stored efficiently is left alone rather than converted into a color photograph.
Already optimized PDFs
If the smaller candidates are invalid, or the saving is under 8 KB and under 5 percent, PDFZaro keeps the original. The page says the PDF is already well optimized. It does not present a 0 percent success, and it does not download a larger rewritten file.
Scanned PDFs
A color or grayscale scan can be reduced by compressing its images. A 1-bit or fax-style scan is not converted to a color JPEG just to show a smaller number. Scanned text is not turned into searchable text. There is no OCR step.
Password-protected PDFs
Encrypted files are rejected before compression. The tool does not ask for a password and does not try to guess one. A damaged file is also rejected. It is not quietly repaired into the download.
Questions
How much can my PDF be compressed?
It depends on what is inside. Photographs and lossless images often shrink. Text and vector pages often do not. A result is offered only when it is a valid PDF and at least 8 KB and 5 percent smaller.
Does compression reduce quality?
Image compression can. Recommended avoids recompressing pictures that are already JPEG. Strong and Maximum trade more image detail for a smaller file. Text that is stored as text stays text.
Will text remain searchable?
Yes, when the original page contains real text, including Arabic text on the files used to test this tool. A scan that is only an image stays an image.
Are my files uploaded?
No. The work runs in your browser. The site does not receive the file bytes, the file name, or the text inside the PDF.
Why did my PDF barely get smaller?
The streams were probably already efficient. PDFZaro then keeps the original instead of pretending the compression worked.
Can I compress a scanned PDF?
Yes, when the scan is a color or grayscale image that can be stored more efficiently. Efficient black-and-white scans are not converted into color images.
Can I compress a password-protected PDF?
No. It is rejected with an explanation. Unlocking files is not part of this tool.
Does it work on iPhone?
The same page is used. Compression needs more memory than a simple merge. A phone can run out of memory on a large file, and the page says so instead of offering a partial download.