PDF Image Compressor

Compress PDF Images Online

Shrink the photos embedded inside a PDF without touching its text, fonts or layout. Quality control, a resolution cap, and a clear per-image breakdown. Nothing leaves your device.

Last updated: August 2026

In-place

Text and Layout Untouched

Reported

What Was Skipped, and Why

No Larger

Ever, Only Kept As Is

Private

No Uploads

Drop your PDF here

One PDF at a time

Your file never leaves this device

How to compress the images inside a PDF

Five steps, all running locally in your browser once you provide a file.

01

Drop your PDF

The PDF library and encoder only load once you provide a file. Nothing is uploaded, it stays on your device.

02

Review what was found

Every embedded image is listed as compressible or skipped, each skip with a specific reason.

03

Set quality and an optional size cap

Quality from 40 to 95, plus an optional longest-side cap from five presets. The cap only shrinks, never enlarges.

04

Compress

Each qualifying image is decoded, resized if needed, and re-encoded in your browser, with per-image progress shown.

05

Download the result

The compressed PDF is ready with the size reduction shown. Text, fonts and layout are untouched.

What actually happens to your PDF

Only the embedded images that can be safely recompressed are touched. Everything else is reported, never guessed at.

Detection before compression

Every embedded image is found and classified first, so you see exactly what will be compressed before anything happens.

Quality and resolution control

A quality slider from 40 to 95 for JPEG recompression, plus an optional cap on the longest side chosen from five fixed presets.

Per-image breakdown

See the before and after size of every image individually, and the total reduction across the whole document.

Text, fonts and layout untouched

Only image objects are ever rewritten. Everything else on every page stays exactly as it was.

What gets skipped, and why

Scanned bi-level images, CMYK images and a few other edge cases are left alone on purpose, each with its own clear reason shown.

Never larger, only kept as is

If recompressing an image would make it bigger, the original is kept and reported as already optimized instead.

What you can do with this tool

Shrink a photo-heavy report for email

A report with a dozen embedded photos can easily exceed an email attachment limit. Recompressing the images alone often solves it.

Reduce a marketing PDF for a website download link

A brochure or one-pager exported at print resolution is usually far larger than it needs to be for a simple website download.

Clean up a PDF exported from a design tool

Design and presentation software often embeds images at full resolution regardless of how small they appear on the page.

Check what is actually taking up space

The per-image size breakdown makes it obvious which specific images are responsible for most of a PDF's file size.

What gets skipped, and why

Scanned bi-level images (JBIG2, CCITT)

Specialized formats for scanned black and white pages. Decoding them reliably in a browser is not something this tool attempts, so they are left exactly as they are rather than risking a broken page.

CMYK images

Detected directly, and through the more common real world case, an embedded ICC color profile reporting 4 channels. Left untouched rather than approximately converted, since that conversion can shift color at print time.

Non-JPEG raw bitmaps

Reconstructing pixels from an arbitrary raw color space and bit depth is real additional risk for comparatively little benefit, since most oversized PDFs are bloated by embedded JPEGs, not raw bitmaps.

Images with a transparency mask

Replacing an image without also correctly handling its separate mask object risks breaking the transparency entirely, so these are left alone.

Why compressing images inside a PDF does not touch anything else

A PDF page does not store an image's pixels directly inside its own content. Instead, the page contains an instruction that essentially says draw the image that lives in object 47 at this position, and object 47 is stored separately elsewhere in the file as what is called an image XObject. Every place across every page that uses that image points at the same object, rather than each place storing its own copy. That structure is exactly what makes replacing an image safe and precise. Recompressing an image means swapping out what object 47 contains, and every page that already pointed at object 47 automatically shows the new, smaller version, with no need to find and rewrite the page content itself.

This is also why the rest of the document is guaranteed to stay untouched. Text is stored as its own separate kind of object, fonts are embedded as their own objects, vector graphics and page dimensions are unrelated structures entirely. None of that is walked or modified by this tool, only the specific objects that are image data and that pass the safety checks described above ever get rewritten.

Why some images are left alone rather than compressed anyway

It would be technically possible to attempt every embedded image regardless of its format, decoding a scanned fax-style image with a fragile, unofficial method, or converting a CMYK photograph to RGB with an approximate formula. Both of those would sometimes work and sometimes produce a subtly broken or discolored result, and there is no way to tell which case you are in until after the fact. Skipping those categories entirely, and saying so plainly in the results, is the more honest choice. A PDF you can trust the output of is worth more than a slightly bigger file that compressed everything, including the images that were never safe to touch in the first place.

If your PDF is a scanned document and this tool reports most of its images as skipped, that is expected rather than a bug, and a general purpose PDF tool that promises to handle every possible embedded format is making a promise it likely cannot keep reliably either. For photo-heavy PDFs, brochures, reports, anything built from embedded JPEGs rather than scanned pages, this tool handles the common case directly and the results are usually substantial. If you're starting from loose photos rather than an existing PDF, you can also combine images into a PDF first, or compress a standalone photo before it ever gets embedded, which avoids the CMYK and mask-skipping edge cases entirely since you're working with the source file directly. If you just need to pull individual pages back out as images afterward, that's what PDF to Images is for, and the metadata viewer can confirm the exact dimensions of any extracted image.

Common PDF image compression mistakes

Expecting a scanned document to shrink much

Scanned pages are usually stored as JBIG2 or CCITT, formats built for black and white scans, not photographs. Those are skipped on purpose rather than risking a broken page. This tool works best on PDFs built from embedded JPEG photographs.

Assuming a print-ready CMYK photo gets compressed

CMYK images are detected and left untouched rather than approximately converted to RGB, since that conversion can shift color at print time. Check the per-image summary for anything reported as CMYK.

Setting quality very low and expecting every image to shrink

An image that's already efficiently compressed may not shrink further even at quality 40. This tool never makes a file bigger to force a change, it keeps the original and reports it as already optimized instead.

Expecting the dimension cap to resize small images up

The longest-side presets are a ceiling, not a target. An image already smaller than the preset you pick stays at its original dimensions.

Trying to adjust quality after compressing without re-selecting the file

Unlike the standalone image compressor, this tool doesn't recompress live after a result appears. Click Compress another PDF and pick the file again, it's fast since the library stays cached, but it isn't automatic.

Expecting a text-heavy PDF with no photos to shrink at all

Only embedded raster images are ever rewritten. A PDF built entirely from text and vector graphics, with no embedded photographs, will show little to no change in size.

Why use ImgTweak?

Runs entirely in your browser, PDF never uploaded
Never makes an image bigger, only keeps or shrinks
Skips risky formats and explains exactly why
Text, fonts and layout stay untouched
Per-image before and after size shown
Free forever, no account needed

Frequently asked questions

Why does my scanned PDF not get much smaller?

Many scanned documents store their pages using JBIG2 or CCITT encoding, specialized formats built for black and white scanned pages rather than photographs. Decoding those formats reliably in a browser is not something this tool attempts, since getting it wrong risks a broken or unreadable page, so those images are left exactly as they were rather than guessed at. If a PDF is mostly photographs embedded as JPEG, the reduction is usually substantial.

Will this affect the text or layout of my PDF?

No. Only the embedded raster images that qualify are touched. Text, fonts, vector graphics, page size, and the position of everything on the page stay exactly as they were, since a PDF page references an image as a separate object rather than storing it inline, replacing that object does not change anything about how the rest of the page is built.

What quality range can I choose?

The quality slider runs from 40 to 95, not the full 1 to 100 range used by the standalone image compressor. This range is deliberately narrower because quality below 40 tends to look poor on photographic content, and there is very little visible difference between 95 and 100 for a JPEG re-encode.

Can I control the image dimensions directly?

You can optionally cap the longest side of every compressible image using one of five fixed presets: 1200, 1600, 2000, 2500 or 3000 pixels. This is a ceiling, not a fixed size, an image already smaller than the preset you choose is left at its original dimensions rather than being enlarged.

Why do some images not shrink much, or at all?

An image that was already compressed efficiently, or is small to begin with, may not have much room left to shrink at a given quality setting. This tool never makes an image larger to force a reduction, if recompressing would produce a bigger file than the original, the original is kept and that image is reported as already optimized rather than replaced.

Is this safe for a PDF I need to print professionally?

Images using CMYK color, the color model print production relies on, are detected and left untouched rather than approximately converted, since that conversion is exactly the kind of change that can look fine on screen and print wrong. If your PDF is intended for professional printing, treat any image this tool did compress as screen-safe, and check the per-image summary for anything reported as CMYK and skipped.

What image types does this tool actually compress?

JPEG images embedded in the PDF, which covers the large majority of PDFs that are unexpectedly large because of embedded photographs. Uncompressed or Flate-compressed raw bitmaps, JPEG2000 images, and images with a transparency mask are currently left untouched rather than risking an incorrect result. Every image the tool finds is reported either as compressed or skipped with a specific reason, never silently ignored.

Can I try a different quality setting after compressing?

Not on the same result directly. Unlike the standalone image compressor, this tool doesn't recompress live when you change a setting after a result appears. You'll need to click Compress another PDF and select the file again. The PDF library and encoder stay cached in your browser from the first run, so re-picking the file is quick, but it is a re-select rather than an instant re-run.

Is my PDF uploaded to a server?

No. Reading the PDF, recompressing its images, and rebuilding the file all happen entirely in your browser. Your file never leaves your device. You can disconnect from the internet after loading the page and the tool still works completely.

Ready to shrink your PDF?

No sign-up. No uploads. Drop your PDF above and download the compressed version in seconds.