Why is my PDF so big?
Drop a PDF to see every byte as a zoomable treemap: images, fonts, page content, tagging structure, metadata, duplicated streams and dead weight left behind by incremental saves.
Files are analyzed in your browser; nothing is uploaded.
What makes a PDF file so large?
A PDF is a container: pages, images, fonts and metadata are stored as separate objects, and a handful of them usually account for most of the file. These are the most common reasons a PDF is bigger than expected.
- Images
- Photos kept at print resolution, screenshots and scanned pages stored losslessly, or images much larger than their size on the page. A single uncompressed scan can weigh several megabytes. Fix: downsample to 150–200 ppi for screen use and store photographs as JPEG.
- Embedded fonts
- Fonts are embedded so the document looks the same everywhere. Embedding a whole font instead of only the characters used, large Chinese, Japanese or Korean fonts, or the same font embedded many times can add megabytes. Fix: embed font subsets, and merge duplicate subsets.
- Incremental saves
- Many editors save changes by appending them to the end of the file instead of rewriting it. Older versions of pages, images and metadata stay inside the file, invisible but still taking up space. Fix: use “Save As”, or an optimizer that removes unused objects.
- Duplicate resources
- A logo, background or letterhead embedded once per page instead of once per document. Fix: an optimizer that merges identical images and streams.
- Hidden data
- File attachments, form data (XFA), page thumbnails, and XMP metadata that grows with every edit.
- Complex vector graphics
- Maps, CAD drawings and detailed charts can contain millions of drawing operations in their page content.
The structure tree (tagging) is often a sizeable part of long documents, but it is what makes a PDF accessible to screen readers. It is worth keeping.
Frequently asked questions
Is my PDF uploaded anywhere?
No. The file is analyzed by JavaScript running inside your browser, and nothing is sent to a server.
What do the colors in the treemap mean?
Each color is a kind of content: images, fonts, page content, structure tree, metadata, file overhead and so on. The area of each block is proportional to its size in bytes. Striped blocks are data that can be removed without changing how the document looks.
What is the “decompressed” size?
Most data in a PDF is compressed. The decompressed size shows how large each part is once its compression is undone (for images, the raw pixel data), which helps spot content that is poorly compressed.
Does it work with password-protected PDFs?
Yes. PDFs that are only restricted by an owner password open directly. For PDFs that need a password to open, you can enter it; it is used only in your browser.