Crop PDF
Trim the visible area of a page - by hand, by shape, or automatically.
This tool runs entirely in your browser. Your file is never uploaded, and you can verify that in your browser's network tab. Verify it yourself: open your browser's network tab and watch. You will see one small request asking whether you have tasks left - a tool name and a hash, never the file.
What this does
Cropping a PDF sets its crop box, which tells a reader which part of each sheet to display. It does not delete anything: the content outside the box is still in the file, and widening the box again brings it back. That is worth knowing before you crop a signature or an account number off something and send it on.
The usual reasons are a scanner that left 15 mm of grey around every page, a document with margins so wide it wastes half a tablet screen, a page that has to fit a slide or an e-reader, or receipts photographed with a desk in the frame.
How it works
- Drop the PDF onto this page and wait for the first page to render.
- Choose the mode: drag the rectangle yourself, let the tool find the content, or crop to a fixed shape.
- For a manual crop, drag the handles, or type what to take off each edge in millimetres, points or inches.
- For an automatic crop, set the breathing room to leave around the content - six points is a sensible start.
- Decide whether to crop every page or only a range, then press Crop.
- Check a page in the downloaded file before you discard the original.
The automatic mode is why most people come here. Each page is rendered small - 400 pixels on its long edge, which is ample, since ink boundaries do not move when you look at them from further away - and every pixel more than about 9 percent away from white counts as content. The bounding box of that content, plus your margin, becomes the crop box. Rendering 300 pages at full resolution to find their margins would cost more than the crop.
Automatic cropping measures each page separately, so pages end up different sizes when their content does. That suits reading on a screen and is awkward for printing, where one tray wants one size; crop by hand or by shape if every page must match. A page with no ink has no box to compute, so it keeps its full size rather than being cropped to nothing, and a document where every page is blank is refused rather than destroyed.
Crop to a shape takes the largest rectangle of the proportions you pick that fits inside the page, centred. A4 is the 1:1.414 shape of the paper itself, so it trims a letter-sized page to those proportions; 16:9 on a portrait page removes a great deal of height, which is the point when the result is going into a slide. Nothing is scaled - only the visible window changes.
Also shrink the page size reduces the media box along with the crop box, so readers and printer drivers that ignore the crop box obey too. It is harder to undo, and it is still not deletion: the content outside is exactly where it was.
Everything happens in your browser: PDF.js renders the pages to measure them and pdf-lib writes the boxes. The pages are never re-encoded, so a scan keeps its original image data at full resolution.
What this tool cannot do
- Cropping hides content, it does not remove it. Everything outside the crop box remains in the file and reappears the moment somebody widens the box. Use Redact PDF when the content must actually be gone.
Questions people ask
- Is the cropped-off content really gone?
- No. Cropping writes a crop box that tells readers what to display; the text and images outside it are untouched in the file and any tool that widens the box gets them back. If you are cropping to hide a signature, an address or a bank detail, use Redact PDF instead, which rebuilds the page from pixels so there is nothing underneath.
- How does the automatic margin trim decide where the content is?
- Each page is rendered at 400 pixels on its long edge and every pixel more than about 9 percent away from white is treated as ink - a threshold chosen so grey scanner paper is not mistaken for content while a pale yellow highlight still is. The bounding box of those pixels, grown by your margin and clamped to the page, becomes the crop box.
- Can I crop only some pages, or crop them differently?
- Yes. Switch Apply to from every page to a range and name the pages; the rest are left as they are. In automatic mode each page in the range is measured from its own content, so a mixed document does not inherit one page's margins.
- Can I undo a crop later?
- Yes, by cropping again with a larger box - nothing was removed, so the content comes back. It is more work if you turned on Also shrink the page size, since the sheet itself was redefined. Keep the original until you have checked the result either way.
- Does the document leave my device to be measured?
- No. The rendering that finds the margins happens on an OffscreenCanvas inside a Web Worker on your machine, and those pixels never leave it. Automatic cropping does have to look at the page - it looks locally, and nothing is transmitted.