About compress PDF
A PDF can carry substantial data in embedded raster images, embedded font programs, and objects stored without compression or duplicated across the file. This tool attempts image re-encoding and structural rewriting; it does not subset embedded fonts. Supported image streams are decoded where possible, downsampled where placement can be measured, and re-encoded as JPEG at your chosen quality. Each replacement is kept only if its stream is smaller, and images below the DPI target can still be re-encoded. If enabled, metadata cleanup targets eight standard Info keys and detaches the catalog XMP reference; custom entries and XMP bytes may remain. The PDF is rewritten with object streams, without deduplicating resources or removing every unused object. These structural and metadata steps do not deliberately change page artwork, while downsampling and JPEG re-encoding discard image information permanently. The rewritten candidate is returned only when smaller; otherwise the original images, metadata and bytes remain unchanged. A text- or vector-heavy document may benefit only from structural rewriting and limited metadata cleanup, so this method may save little. Little or no saving does not establish the smallest achievable size.
How to compress PDF
- 01
Add your PDF
Drop one file onto the drop zone or use Choose file. It is read into the tab, not sent anywhere.
- 02
Choose image settings
Start with the JPEG quality and resolution fields. They override the level selector on this page; changing the level alone does not change the compression settings.
- 03
Fine-tune if you want
Resolution and JPEG quality are independent. A lower DPI target can remove pixels from supported images with measurable placement; lower JPEG quality can introduce artefacts. Compare detailed images at the zoom or print size you need.
- 04
Compress and compare
Press Compress PDF, check the before-and-after size, and download. Re-run with different settings if the trade-off is not right.
What this tool does
- Independent control of resolution, JPEG quality, colour and metadata rather than one opaque slider
- Before-and-after file size shown so you can judge the trade-off instead of guessing
- Images below the DPI target keep their pixel dimensions but may still be re-encoded if a smaller stream is produced
- Object-stream rewriting runs on every attempt; limited metadata cleanup runs only when enabled, and candidate changes are discarded if the PDF is not smaller
- Runs in the tab with no upload; browser-processing limits are 250 MB and 5,000 pages per PDF
Limitations worth knowing
Every PDF tool has constraints. Stating them plainly is more useful than discovering them halfway through your work.
- Without supported raster images to re-encode, any saving comes from structural rewriting and limited metadata cleanup. Text- and vector-only PDFs may save little, but no fixed reduction can be predicted.
- Image downsampling and JPEG re-encoding are lossy and cannot be undone. Keep your original if the document matters.
- Embedded fonts are kept whole rather than subsetted, so a file that is large because of its fonts sees little benefit.
- Encrypted PDFs are rejected. Supply an unencrypted copy; this page has no password prompt.
How your file is handled
This tool runs entirely inside this browser tab. When you choose a file, your browser reads it from your own disk and hands the bytes to JavaScript running on this page — no network request carries your document anywhere. You can confirm that yourself: open your browser’s developer tools, switch to the Network panel, and run the tool. You will see no upload.
Nothing is stored after the fact. Closing or reloading this tab discards the file, the result and everything derived from them, because none of it ever left your machine. Read how local processing works.
Questions about compress PDF
How much smaller will my file get?
There is no fixed percentage. Image content, existing compression, browser decoding support and file structure all affect the result. Scans and photographs can offer savings, while text-heavy files may mainly benefit from structural rewriting. Run an attempt and read the returned-file size: if the candidate is not smaller, the original is returned unchanged.
What is the difference between DPI and JPEG quality?
For a supported image with measurable placement, the DPI target limits the pixel dimensions used for downsampling. Halving both dimensions leaves about one quarter of the pixels, but not every image is resampled. JPEG quality controls the encoder independently, so images below the DPI target may still be re-encoded. Lower settings can reduce detail or introduce artefacts; inspect the result at the intended size.
Is compression reversible?
Accepted downsampling and JPEG re-encoding permanently discard image information, so keep the original. Structural rewriting and supported metadata cleanup do not deliberately alter page artwork, but removed metadata is not recoverable from those fields. Cleanup is not secure erasure because other copies may remain. If the candidate is not smaller, the original is returned with no candidate changes applied.
Why did my PDF barely shrink, or stay the same size?
This method may find little to save in text-heavy files, already-compressed images or images the browser cannot decode. Larger image replacements are rejected. If the whole rewritten PDF is not smaller, the original bytes are returned unchanged, including their metadata. A no-saving result describes this attempt, not the smallest size another method could achieve.
Are my files uploaded anywhere?
No. The document is decoded and rewritten in your browser tab. No request carrying file content leaves your device, which you can verify in your browser's network inspector.
Tools that pair with this one
- Reduce PDF File SizeTry smaller image settings, then compare the returned size and appearance with your target.
- PDF OptimizerTry structural rewriting and image compression, then check the returned file and reported saving.
- Compress PDF for EmailTry reducing an attachment, then check its size against both mail providers' limits.
- PDF Size AnalyzerA byte-level breakdown of where your PDF weight actually is.
- Batch Compress PDFCompress a whole folder of PDFs in one pass and get a ZIP back.
- Merge PDFCombine several PDFs into a single document, in the order you choose.
Read more about this
- How to compress a PDFCompression is four independent levers, three of them lossy. This guide explains what each one does to your pages so you can choose deliberately rather than guess.6 min guide
- How to reduce PDF file size to meet a limitWritten for the case where a number is imposed on you — an email cap or an upload form. How to converge on a target quickly and what to do when you cannot reach it.6 min guide