RunLocalTools

Compress PDF Online Free — Shrink Scanned & Image-Heavy PDFs

Compress PDF files free, right in your browser — no upload, no account, no file-size limit. Best for scanned documents and image-heavy PDFs; text pages are left untouched.

What it does

This tool shrinks PDF file size by recompressing pages that are essentially scanned images — the case that usually makes a PDF balloon to tens of megabytes. Drop in one file or a whole batch, pick a compression preset, and download smaller versions, either one at a time or all together as a zip.

How it works

Rather than blindly rasterizing every page (which would also flatten and shrink any real, selectable text), this tool looks at each page individually. A page that’s essentially a photo or scan — little or no extractable text — gets re-rendered at your chosen resolution cap and re-encoded as a JPEG at your chosen quality, which is where the size savings come from. A page with real paragraph text, even one that also has a photo on it, is left completely untouched: copied through byte-for-byte, so nothing you could select, search, or copy gets rasterized away.

Three presets cover most cases — Web (smaller, for on-screen use), Balanced, and Print (higher quality, larger) — or switch to Custom for direct control over JPEG quality and the maximum image dimension. Every file is also checked afterward: if compressing wouldn’t actually make it smaller, you get the original back rather than a “compressed” file that’s the same size or bigger.

If you’re not sure whether your PDF is actually a scan or has real text worth preserving, pdf-scan-look can tell you before you compress.

How to use it

  1. Choose a preset — Web, Balanced, or Print — or switch to Custom for a quality slider and a maximum image size.
  2. Drag in your PDF (or several at once for a batch).
  3. Click Compress all. Each file shows its progress and, when done, exactly how much space it saved — or a note that it was already about as small as it could get.
  4. Download files individually, or grab everything at once as a zip.

Your files pick up right where you left off if you refresh the page mid-batch — nothing is uploaded anywhere, it’s just saved locally in your browser so you don’t lose your place.

Supported files & limitations

  • Works on standard PDFs. Password-protected files can’t be opened here and are skipped with a clear note — remove the password first (or use another tool to do so), then try again.
  • Only pages that read as “essentially a scanned image” are recompressed. A page mixing a photo with real body text is left alone on purpose, to protect its selectable text — so a PDF like that will show a smaller size reduction than a pure scan would.
  • If you need to combine several PDFs into one before or after compressing, pdf-merge handles that separately.
  • If your PDF started life as a Word document, converting it fresh with docx-pdf sometimes produces a smaller file than compressing an already-exported one.

Privacy

Nothing is uploaded. The PDF never leaves your device — compression happens entirely in your browser. Files you add are kept locally (in your browser’s storage) only so a refresh doesn’t lose your batch; a “Clear saved files” button removes them whenever you want.

FAQ

Will this make my text blurry or hard to select?

No — pages with real text are left untouched entirely. Only image-only/scanned pages are recompressed, so any page you can currently select text on will still work exactly the same afterward.

Why didn’t my file get any smaller?

Either the file is mostly text pages already (nothing to recompress), or it was already efficiently compressed — in that case you get your original file back rather than a same-size “compressed” copy.

Is there a file size or page count limit?

No hard limit, but very large batches or very high page counts will take longer to process since everything runs in your browser rather than on a server.

Does this work on password-protected PDFs?

Not directly — they’re detected and skipped with a note so nothing fails silently. Remove the password first, then compress.

What’s the difference between the Web, Balanced, and Print presets?

They trade off file size against image quality: Web compresses hardest (best for emailing or on-screen viewing), Print keeps the most quality (best if the file might be printed), and Balanced sits in between. Custom mode gives you direct control if none of the three fit.

Can I compress just specific pages?

Not in this version — it’s whole-file, page-by-page automatic detection. If you need to extract specific pages first, pdf-merge‘s split mode can pull out a page range before you compress it.