PDF Page Dimensions & Box Inspector
Inspect a PDF's MediaBox, CropBox, BleedBox, TrimBox and ArtBox in points, inches and millimeters. Everything runs in your browser — your file is never uploaded anywhere.
Drop a PDF file here, or click to browse
It stays on your device — nothing is uploaded.
Why a PDF can have five different page sizes at once
MediaBox is the full digital “sheet” a page is built on. CropBox is what most viewers actually display, and it can be smaller than MediaBox. BleedBox marks how far ink is allowed to run past the trim edge for designs that print edge-to-edge. TrimBox is the real finished-size cut line — the one a print shop's RIP actually checks. ArtBox marks the meaningful content area other layout tools should align against. A file that looks completely normal in a PDF viewer, which usually renders CropBox or MediaBox, can still carry a missing or mismatched TrimBox that only shows up once something actually inspects the box dictionary.
What “inherited” means for a box that isn't set
Per the PDF specification, only MediaBox is required. CropBox defaults to MediaBox when it isn't explicitly set, and BleedBox, TrimBox and ArtBox each default to CropBox when they aren't set. That fallback chain is exactly why a page can silently ship without a real trim size defined at all — it just quietly inherits the full CropBox as its trim line, which is rarely what was actually intended for a print job.
How to use this inspector
- Add a PDF file.
- Click "Inspect Page Boxes".
- Review every page's five boxes, and switch units between points, inches and millimeters.
- No upload
- Your PDF's page dictionary is read entirely in your browser — nothing is sent to a server.
- Box inheritance follows the PDF spec
- CropBox defaults to MediaBox; BleedBox, TrimBox and ArtBox each default to CropBox when not explicitly set on the page.
Questions
Why does my PDF look correct in Acrobat but fail print-shop preflight?
Most viewers display CropBox (or MediaBox if CropBox isn't set) — they don't typically call out TrimBox or BleedBox visually at all, so a file with a missing or mismatched TrimBox can look completely normal on screen while a print shop's RIP flags it immediately during preflight, because the RIP checks TrimBox specifically to determine where to cut.
What does it mean if this tool shows TrimBox as "inherited" rather than explicit?
It means the PDF's page dictionary doesn't set a TrimBox at all, so per the PDF spec it defaults to CropBox (or MediaBox, if CropBox is also unset). That's not necessarily wrong for a digital-only document, but for anything going to print, an inherited TrimBox usually means the finished trim size was never explicitly defined — worth confirming before it ships to a press.
My bleed looks fine on one page but flagged on another — why?
PDF boxes are set per page, not per document, so a multi-page file assembled from different source documents (common with merged proofs, or pages added at different times) can easily end up with inconsistent boxes across pages even though the file looks uniform when scrolling through it. This tool reports every page's boxes independently for exactly that reason.
Is my file uploaded anywhere to check this?
No. The PDF's page dictionary is read entirely in your browser — nothing is ever sent to a server, and the file never leaves your device.