See what makes your PDF large
See exactly where a PDF uses its bytes without uploading or changing it. The tool follows the document graph and matches images, font programs and content streams to the pages that use them. The report separates images, fonts, page content, metadata, embedded files, old objects and file structure, checks that the totals equal the source file, and names the one change worth making.
How to find what makes a PDF large
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Choose a PDF
Press Choose a PDF, or drop one on the page. The file stays in this browser tab.
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Walk the PDF objects
The tool follows the document graph and matches images, font programs and content streams to the pages that use them.
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Reconcile every byte
Parsed object sizes are apportioned to the physical file. Headers, indexes and other wrapping stay visible as their own category.
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Inspect and act
Review the largest objects and follow one recommendation based on the part that actually takes the most space.
What the numbers mean
Every number is the stored byte count, not the decoded one. A JPEG can decode into many megabytes of pixels and still store far fewer, so the report always states what the file holds. Object headers, cross-reference data and trailers appear as their own category rather than being spread silently across the others, and the categories plus that wrapper must equal the exact source byte count. When they do not, the run fails instead of reporting.
PDF parsers normalize object syntax and object streams, so parsed sizes are apportioned back to the physical file. Analyze the file size before you compress: the breakdown names the category that holds the bytes, and the table below says whether compression can move it.
What each size category counts
| Category | What it counts | Compression moves it |
|---|---|---|
| Images | What it countsPhotos, scans and logos at their stored size, not their decoded pixel count. | Compression moves it Yes. Yes Compress PDF re-encodes placed images at 150 DPI. |
| Fonts | What it countsEmbedded font programs. A full font costs the same whether a page draws 12 glyphs or 1,200. | Compression moves it Partly. TrueType only The font arm subsets embedded TrueType to the glyphs the pages draw. Type 1 and CFF programs are left alone. |
| Page content | What it countsThe drawing instructions for each page: text runs, vector art, positions. | Compression moves it Partly. Rarely These streams are already compressed. A large number here usually means vector art, not text. |
| Embedded files | What it countsAttachments carried inside the PDF, such as the spreadsheet a chart came from. | Compression moves it No. No Remove the attachment or the bytes stay. |
| Metadata | What it countsXMP packets, document info and the producer trail. | Compression moves it No. No Kilobytes, not megabytes. Remove PDF metadata clears it for privacy, not for size. |
| Unreferenced objects | What it countsObjects left by earlier saves that the current document no longer reaches. | Compression moves it Partly. Usually A clean save can drop them. It can also invalidate a digital signature. |
| PDF structure | What it countsThe page tree, outlines, annotations and form field definitions. | Compression moves it No. No A fixed cost of what the document is, not of how it was saved. |
| File wrapper | What it countsObject headers, cross-reference data and trailers. | Compression moves it No. No Format overhead. It moves only with the number of objects. |
The breakdown reports the split. It never rewrites the PDF.
What to do with the answer
A breakdown is a diagnosis, not a fix. Once you know which images, fonts or content streams carry the weight, How to compress a PDF covers the ordinary route, and Compress a PDF without losing quality covers what can be reduced with no visible change and what cannot.
Questions
- Does the size breakdown change my PDF?
- No. This tool reads the file and produces a report. It does not write a new PDF.
- Do the categories add up to the exact file size?
- Yes. The receipt checks that the categories and file wrapper equal the source byte count exactly.
- Why is file wrapper a category?
- A PDF also contains object headers, cross-reference data, trailers and other physical wrapping. Parsed objects do not retain every original byte offset, so that difference is shown instead of hidden.
- Can it tell me which image is large?
- Yes. The largest-object list includes page location, pixel dimensions, placed DPI and codec when that information is available.
- Does the size breakdown upload my PDF?
- No. The PDF object graph, page matches and size report stay in this browser tab.
- What should I do with the result?
- Start with the single change the report names. That is usually one oversized image, or a font embedded in full where a subset would do. Compress PDF acts on the first case; rebuilding the document from its source acts on the second. Run the breakdown again afterwards to watch the categories move.
Related tools
Each runs in a browser tab like this one, reads its own output back before the download, and needs no account. The footer links every tool.
- Compress PDF Hit a size target
- Repair PDF Rebuild a broken file
- Extract images Save original pictures
- Merge PDFs Several PDFs into one
- Organize pages Split, reorder, delete
- Rotate & crop Pages upright, margins cut
Where to go next
- Compress PDF Make a PDF smaller without turning its text into a picture.
- Extract images from PDF Save the separate pictures stored inside a PDF at their original resolution.
- PDF document repair Get pages back out of a PDF that will not open.
- How it works Understand what runs in the browser tab, what it checks, and what it never sends.