PDF Compressor — Shrink PDFs Without Uploading
Shrink PDFs in your browser — pick image format, quality and DPI; text stays sharp and nothing is uploaded.
Runs entirely in your browser — nothing you paste is uploaded or stored.
What is pdf compressor?
This tool makes a PDF smaller entirely inside your browser. Almost all of a typical PDF's size is its images — scanned pages, photos, screenshots — so the compressor re-encodes every embedded image at the format, quality and resolution you choose, while leaving text, fonts and vector drawings exactly as they were: the result is still searchable and selectable, never a stack of flattened page pictures. Three presets cover most needs, and Advanced options expose the individual levers: image format (JPEG, lossless, or match each image's original), JPEG quality, a maximum image resolution in DPI, grayscale conversion, and removal of metadata and embedded thumbnails. On top of that it always applies the free wins — recompressing text and font streams at maximum level, merging duplicate images and fonts, deleting unused objects left behind by earlier edits, and writing compact object streams. The file is processed in a background worker on your device and is never uploaded, which matters for contracts, invoices, IDs and anything else you'd rather not hand to a random website.
When to use it
- Getting a scanned contract or form under an email attachment limit or an upload portal's size cap.
- Shrinking a photo-heavy report or slide-deck export before sharing it with a team.
- Compressing confidential documents (IDs, bank statements, medical records) without sending them to a third-party server.
- Converting a colour scan of a black-and-white document to grayscale for a much smaller archive copy.
- Stripping author names, editing-app details and other metadata from a PDF before publishing it.
How to use this tool
- Drop a PDF onto the tool, or choose one from your device — compression starts immediately.
- Pick a preset — Light for print quality, Balanced for everyday sharing, Strong for the smallest file.
- Open Advanced options to choose the image format, drag the JPEG quality slider, or set a maximum resolution.
- Scroll through the whole compressed document in the built-in preview, switching to Original to compare any page.
- Check the before/after comparison of the document's largest image to judge whether the quality holds up.
- Press Download PDF to save the compressed copy — your original file is never modified.
Example
A one-page report with a large photo, compressed with the Balanced preset.
Input
A one-page PDF with a headline, body text and a 2400×1600 photo saved as 95% JPEG.Output
The same PDF with the photo re-encoded as 70% JPEG at 150 DPI (about 1650×1100 pixels) — typically 75-90% smaller, with the text still selectable.Press "Load example" to generate this sample PDF and see the real size reduction and before/after comparison yourself.
Choosing format, quality and resolution
JPEG gives the smallest files and is the right choice for photos and scanned pages. Lossless never changes a pixel, so it only saves space through downsampling and grayscale conversion — use it when an image contains fine text or line art that must stay crisp. Match original is the careful middle ground: images that were already JPEG are re-encoded at your chosen quality, and lossless images (screenshots, diagrams) stay lossless. Images that carry transparency are always kept lossless whatever you choose, since JPEG artefacts in a transparency mask show up as halos around edges.
The resolution cap is measured against the document’s largest page: at 150 DPI an image drawn across a full Letter or A4 page keeps about 1650 pixels on its long side. That’s sharp on screen and fine for office printing; choose 300 DPI if the PDF is headed to a professional printer.
What powers this tool
PDF parsing and writing use pdf-lib (MIT
licensed). Stream compression uses fflate (MIT
licensed). JPEG decoding and encoding use your browser’s own built-in image codecs. All of
it runs locally on your device.
Frequently asked questions
Is my PDF uploaded to a server?
No. The PDF is read, compressed and rebuilt entirely in your browser, in a background worker so the page stays responsive. Nothing you choose is transmitted anywhere — you can disconnect from the internet after the page loads and the tool still works.
Why can't I choose WebP, AVIF or PNG as the image format?
A PDF can only store images in a few specific encodings — JPEG, JPEG 2000, and raw pixels compressed with Flate (the same deflate algorithm used inside PNG files). WebP and AVIF images simply aren't allowed inside a PDF, and a PDF reader couldn't display them. The Lossless option here is the PDF equivalent of PNG, using the same row filters and compression a PNG file uses internally. JPEG 2000 isn't offered because browsers can't encode it.
Which settings give the smallest file?
Resolution is usually the biggest lever — a 300 DPI scan capped at 150 DPI has a quarter of the pixels. After that, a lower JPEG quality and grayscale conversion help most. The Strong preset combines 96 DPI with 50% JPEG quality. For documents with mostly text and few images, expect modest savings — text and vector graphics are already compact, and this tool deliberately never rasterizes them.
Will the text still be searchable and selectable?
Yes. Only embedded images are re-encoded; text, fonts and vector drawings are kept exactly as they were (their streams are only losslessly recompressed). Some online compressors "print" every page into an image, which makes a smaller file but destroys text selection, search and accessibility — this tool never does that.
Why did my PDF barely shrink, or not shrink at all?
Either the PDF is mostly text and vectors, which are already compact, or its images are in formats this tool leaves untouched — JPEG 2000, JBIG2 and CCITT fax scans (the last two are already extremely efficient for black-and-white pages), or CMYK print images, whose colours could shift if re-encoded in a browser. The results panel lists exactly which images were skipped and why. If the rewritten file wouldn't be smaller, the tool tells you instead of handing back a larger "compressed" file.
Can it compress a password-protected PDF?
No — an encrypted PDF can't be rewritten without its password, and browser PDF libraries can't re-encrypt the result. Open the file in a PDF viewer, use "Print to PDF" to save an unprotected copy, and compress that instead.