Rasp

Compress a PDF

Shrink a scan until it fits an attachment limit. Everything happens on your own machine — the document is never uploaded.

Ready
Uploaded0 B
Target

How do I reduce the file size of a PDF?

Drop the PDF onto this page, pick a target, and download the smaller file. Each page is re-rendered at a lower resolution and re-encoded, which is why this works best on scans. Selectable text becomes an image in the result, so the page warns you when your document contains any.

How to do it

  1. Add your PDF. Drag it onto the panel or click to choose. Scanned documents are what this tool is built for.
  2. Pick a target. Balanced suits email and upload forms. Smallest goes further at visible cost. Careful keeps fine detail for documents that still need to be read closely.
  3. Check the warning if one appears. If your PDF contains selectable text, the page says so. Compressing turns that text into pixels — fine for a scan, a real loss for a text document.
  4. Download the result. Your original file on disk is never modified, so you can try a different target whenever you like.

At a glance

Works onPDF documents
Where it runsIn this browser tab. The file is not uploaded
File size limitNone imposed — your device memory is the ceiling
CostFree
Account neededNo
WatermarkNone
Works offlineUsually after first use, but not guaranteed — there is no offline app

What it actually produces

Measured, not estimated. A procedurally generated 2400×1600 (3.8 MP) test image built to carry photographic entropy: value noise across nine octaves down to near-pixel scale, a dense field of small high-contrast features, a smooth gradient, hard edges and light grain. It is not a photograph — it is reproducible, which a photograph is not. Each figure below comes from running that image through this page.

InputOutputChange
376 KB174 KB54% smaller

Your own files will differ — a photograph, a screenshot and a diagram compress very differently. The point of a fixed image is that the formats can be compared with each other, not that your result will match.

What this tool actually does

It re-renders each page at a lower resolution, encodes it as a JPEG, and assembles a new PDF from those images.

That is worth understanding before you use it, because it explains both why it works so well on one kind of file and why it is the wrong tool for another.

Best case: a scan

Scanned PDFs are the files that are actually too large, and they are the perfect input here.

A scan is already a photograph of each page — the letters exist as pixels, not as characters. Re-rendering it at a sensible resolution and re-encoding loses nothing you had, because you never had selectable text to begin with. A 40 MB scanned contract becoming a 3 MB one costs you nothing but resolution you were not using.

Worst case: a text document

If your PDF has real text — exported from a word processor, say — compressing it here turns that text into pixels.

The result looks similar and behaves quite differently. It can no longer be selected, searched or copied. Links stop working. Screen readers cannot read it. And the file may well come out larger, because storing crisp text as JPEG images costs more than storing the characters did.

So the tool checks. When it finds a text layer, it says so plainly before you download, and you can decide.

That check is the reason this page exists rather than a simpler one: a compressor that silently destroys searchable text would be the most damaging thing this site could ship, because the damage is invisible until someone needs to search the document.

Choosing a target

  • Balanced — for email and upload forms. This is what most files need.
  • Smallest — when you are against a hard limit and the document only has to be readable on screen.
  • Careful — when fine print, a signature or a stamp still has to be legible.

Each target re-renders from your original file rather than from the previous result, so you can try all three without compounding anything.

What this tool cannot do

Said plainly, because the alternative is more useful than a hopeful answer.

It cannot recompress the images inside a PDF while leaving its text intact. That requires rewriting the document’s object streams, which is a substantially larger piece of work than rasterising.

If you need that — a text-heavy PDF with a few large images, where the text must stay real — Ghostscript is the right tool and runs entirely on your own machine:

gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook \
   -dNOPAUSE -dBATCH -sOutputFile=small.pdf large.pdf

It also cannot run OCR, so a scan will not gain searchable text by passing through here.

Other routes to a smaller file

Sometimes the best compression is not compression at all:

The full picture, including where each route applies: how to make a PDF smaller.

Nothing is transmitted

Rendering runs on PDF.js, the rebuild on pdf-lib, both inside this browser tab.

The PDFs worth compressing are contracts, statements, medical letters and identity documents. The Uploaded readout beside the result measures this page’s own outbound network calls and reads 0 B on success — a measurement rather than a promise.

Questions

How does this compress a PDF?
By re-rendering each page at a lower resolution, encoding it as a JPEG, and building a new document from those images. That is why it works so well on scans, whose pages were already images, and why it changes the nature of a text document.
Will my text still be selectable afterwards?
No. Every page becomes an image, so text can no longer be selected, searched or copied, and links stop working. For a scanned document that costs nothing — the text was already pixels. For a text PDF it is a real loss, which is why the page checks and warns you.
Why is my scanned PDF so large in the first place?
Because a scan is a photograph of each page, stored inside the document. Ten scanned pages are really ten photographs, and at scanner or phone-camera resolution each can be several megabytes.
Which target should I choose?
Balanced for email and upload forms — it is the setting most files need. Smallest when you are up against a hard limit and the document only has to be readable on screen. Careful when fine print or a signature still has to be legible.
Will the result always be smaller?
No. A PDF that is already efficient — a text document with no images — may come out larger, because turning crisp text into JPEG images costs more than storing the characters did. The size readout tells you either way before you download.
Is my document uploaded?
No. The rendering, the re-encoding and the rebuild all happen in this browser tab. The Uploaded readout beside the result measures the page's own outbound traffic, so a successful run reads 0 B. That matters here more than anywhere else on the site — the PDFs worth compressing are usually contracts and statements.
Is there a page limit?
None imposed. Long documents take proportionally longer, since every page must be fully rendered before it can be encoded, and use more memory.
Will there be a watermark?
No. Nothing is stamped onto the pages and no target is held behind a paid tier.
Can I compress without turning text into images?
Not with this tool. Recompressing the image streams inside a PDF while leaving its text intact requires rewriting the document's object streams, which is a much larger piece of work. Ghostscript does it well and runs entirely on your own machine.
Does it work on password-protected PDFs?
Documents that only restrict editing will usually work. A document that needs a password to open cannot be read without it. Remove the password in your PDF reader first.

Sources

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