# Compress PDF > Shrink a PDF in your browser. See which pictures use the space, then re-encode them at 150 or 200 DPI, or tidy the file losslessly. Nothing uploaded. - URL: https://bytescope.dev/en/pdf-compress/ - Locale: en · Also: [ja](https://bytescope.dev/ja/pdf-compress.md) · [zh-Hant](https://bytescope.dev/zh-Hant/pdf-compress.md) - Runs: Your files never leave your browser — all processing is local. - Requires: Any modern browser (Chrome, Edge, Firefox, Safari), desktop and mobile. - Updated: 2026-09-08 ## What it does A phone scan of a three-page form can weigh 18 MB when the portal allows 5. Most of that weight is pictures, so this page reads the file first and lists every picture: its size, its effective resolution (pixels divided by the size it is printed at), its encoding and its share of the bytes. Only then does it estimate what re-encoding would save, and you decide whether to run it. ### Two levels and one resolution choice Level 1 rewrites the file with compressed object streams and drops objects nothing refers to. Pictures stay byte for byte the same, and the saving is usually small. Level 2, the default, re-encodes oversized JPEG and 8-bit pictures as JPEG at quality 75, scaled down to 150 or 200 DPI for where they are printed. A picture that would not get smaller is kept. Pictures with transparency masks, CMYK colour, other bit depths, or JBIG2, JPEG 2000 and CCITT encoding stay as they are, and the page gives the reason for each one. ### Honest limits Vector text and PDFs exported from Word or slide tools carry few pictures, so they barely shrink, and the analysis says so. Re-encoding is lossy: at 150 DPI small print can soften, so compare it in your PDF reader before you send it. Digital signatures stop validating after any change. There is no target size; the tool does what the picture rules allow and reports what it got. ## Limits Does not promise a target size, does not shrink vector text or Word and slide exports much, does not re-encode CMYK, JBIG2, JPEG 2000 or CCITT pictures, does not keep digital signatures valid, does not open password-protected PDFs, and does not keep form fields or bookmarks in its page-picture mode. ## FAQ ### Is my PDF uploaded anywhere? No. The file is analysed and rewritten by JavaScript in this tab. Nothing is sent to a server, so a confidential form or scan stays on your device. ### Why did my PDF barely shrink? Most such files are mostly text and vector drawings with few or no pictures. The analysis shows the picture share before you run anything; when it is small, no setting can save much. PDFs exported straight from Word or a slide tool are the usual case. ### Which level should I pick? Level 2 at 150 DPI for scans and photos you are going to send online. Level 1 when you do not want any picture changed at all. Either way, compare the result in your reader before you send it. ### Can I set a target size such as 5 MB? No. The tool does not promise a size. It shows an estimate before you run it and the real before-and-after sizes afterwards, and you can change the resolution and try again. ### Does the original file change? No. The compressed copy is a separate download, and the original stays where it was. Nothing is kept after you close the tab. ## Related tools - [Merge PDF](https://bytescope.dev/en/pdf-merge.md) — Join several PDFs into one file. - [Split PDF](https://bytescope.dev/en/pdf-split.md) — Cut a PDF into parts, or keep only the pages you need. - [Images to PDF](https://bytescope.dev/en/images-to-pdf.md) — Turn photos and scans into a PDF, one picture per page. - [Remove PDF Metadata](https://bytescope.dev/en/pdf-metadata.md) — Check and remove the author, producer and dates in a PDF. - [PDF OCR](https://bytescope.dev/en/pdf-ocr.md) — Add a searchable text layer to a scanned PDF. - [Compress Image](https://bytescope.dev/en/image-compress.md) — Shrink JPEG, PNG and WebP images before you put them in a PDF.