Analyze PDF file size
What Analyze PDF file size actually does
A PDF compressor can make a file smaller without explaining what it changed. This analyzer starts with diagnosis: it counts unique decoded images, follows their page placements, measures source pixels and effective resolution, and points to likely scan or over-resolution problems. The companion CLI goes deeper by attributing exact stored bytes to image, font, page-content, form, and overhead categories.
How to use it
- Choose the large PDF; PDF.js inspects its pages and raster image operators locally.
- Review unique images, repeat placements, decoded pixel memory, effective PPI, and focused suggestions.
- Download a JSON diagnosis, or run the CLI when an exact raw-stream byte budget is required.
Useful for
- Find full-page scans or oversized photographs before choosing compression settings.
- Explain why a seemingly simple report is much larger than expected.
- Separate image problems from likely font, vector, attachment, revision, or structural overhead.
Limits worth knowing
- Browser analysis measures decoded images and placements, not the compressed byte length of each stored PDF object.
- PDF.js may not expose every unusual image stream or malformed object.
- The analyzer diagnoses likely causes; it does not alter or compress the source file.
Questions people ask
Why is my PDF file so large?
Common causes include full-page scans, photographs stored at far more pixels than their placed size needs, embedded fonts, attachments, complex vector content, and incremental saved revisions. This browser report measures the image side; the CLI attributes exact stored bytes across all major stream categories.
Does decoded pixel memory equal PDF file size?
No. Decoded memory estimates the working pixels required to display images. Stored streams may be much smaller because JPEG, PNG-style filters, and other PDF compression are applied.
Is the PDF uploaded?
No. Inspection runs in this tab and the site has no file-upload endpoint.