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PDF Image Inspector

See the real resolution of every image in a PDF, and the DPI it actually prints at.

Processed locally in your browser. Your file is not uploaded to any server. How this works

  1. 01Add your file
  2. 02PDF Image Inspector
  3. 03Download

Runs in your browser · nothing uploaded

About PDF image inspector

Images in a PDF are objects with a fixed pixel size, drawn into whatever rectangle the page content stream asks for. The two numbers are independent, and the relationship between them is the single most useful figure in print and web production: effective DPI, which is the image pixel width divided by the placed width in inches. A 2000-pixel-wide photograph placed in a two-inch box is being drawn at 1000 DPI. No press needs that and no screen can show it — the pixels are paid for in file size and thrown away at output. The same photograph stretched across an eight-inch page is 250 DPI, which is sensible for print. This tool reports both numbers for every image object so you can see which ones are wasting bytes and which are genuinely too coarse for the size they are used at, and it reports the colour space and compression filter alongside, since those decide what re-encoding is safe.

How to PDF image inspector

  1. 01

    Load the PDF

    Image XObjects are collected from page resources across the document, with reuse detected.

  2. 02

    Read the effective DPI column

    Compare it against your output target: roughly 300 DPI for press, 150 for office printing, 72 to 150 for screen.

  3. 03

    Spot the outliers

    Anything far above target is wasted weight; anything far below will look soft at that size.

  4. 04

    Act on it

    Use the compressor to downsample, or the image extractor if you want the originals at stored resolution.

What this tool does

  • Stored pixel dimensions per image object, independent of how large it is drawn
  • Effective DPI computed from pixel width divided by placed width in inches, per placement
  • Colour space per image: DeviceRGB, DeviceCMYK, DeviceGray, Indexed, ICCBased or separation
  • Bits per component, and soft-mask or stencil-mask presence for transparency
  • Compression filter per image: DCTDecode for JPEG, JPXDecode for JPEG 2000, FlateDecode for lossless, CCITTFaxDecode and JBIG2Decode for bilevel scans
  • Reused images identified so a logo placed on forty pages is counted once, with the DPI range across its placements
  • Stored byte size per image, so the heaviest offenders sort to the top

Limitations worth knowing

Every PDF tool has constraints. Stating them plainly is more useful than discovering them halfway through your work.

  • Effective DPI is per placement. An image used at several sizes has several values, and the report gives the range rather than a single figure.
  • Images drawn with a rotation or a skewed transformation matrix report an approximate effective DPI, since the placed rectangle is not axis-aligned.
  • Vector artwork has no resolution and therefore no DPI. It is not listed here, and scaling it is lossless.
  • This inspects and reports; it does not resample. Downsampling is the compressor's job.
  • A page that is a single full-page scan reports one large image, which is the expected signature of a scanned document rather than a fault.

How your file is handled

This tool runs entirely inside this browser tab. When you choose a file, your browser reads it from your own disk and hands the bytes to JavaScript running on this page — no network request carries your document anywhere. You can confirm that yourself: open your browser’s developer tools, switch to the Network panel, and run the tool. You will see no upload.

Nothing is stored after the fact. Closing or reloading this tab discards the file, the result and everything derived from them, because none of it ever left your machine. Read how local processing works.

Questions about PDF image inspector

How is effective DPI calculated?

Image pixel width divided by the width in inches at which the image is drawn on the page. A 1500-pixel image placed across five inches is 300 DPI. The same image squeezed into 1.5 inches is 1000 DPI. Only the second number depends on the layout, which is why an image can be simultaneously high-resolution and badly used.

What DPI do I actually need?

For offset or digital press, about 300 DPI at final size is the usual specification, with line art and bilevel scans wanting much more. For office printing, 150 is generally indistinguishable. For screen-only PDFs, 72 to 150 is ample. Anything substantially above the target for its medium is weight you are carrying for no visible benefit.

Why is my PDF so large when the images look ordinary?

Usually because they are stored far larger than they are shown. A camera image dropped into a document and scaled down on the page keeps every original pixel in the file. Sort this report by stored byte size, look at the effective DPI of the top few entries, and you will normally find the whole problem in two or three objects.

Can I get the images out at full resolution?

Yes — the image extractor pulls the embedded image objects themselves, at the resolution stored in the file, rather than screenshotting pages. That is a different operation from converting pages to JPG, which rasterises the whole rendered page including text.

What does a soft mask mean in this report?

It means the image carries a separate greyscale channel controlling per-pixel transparency, which is how a cut-out photograph or a soft drop shadow is represented. It matters for two reasons: the mask is extra image data contributing to file size, and transparency is one of the constructs that archival profiles and older print workflows dislike.

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