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Deskew Scanned PDF

Measures how far each page is rotated by looking at how sharply its text lines fall into rows, then rotates it back. Worth running before OCR, because a crooked page reads badly.

Local processingAccepts PDFUp to 100 MB

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How this tool works

  1. 1Each page is rendered in grayscale and its dark pixels projected onto the vertical axis at a range of angles.
  2. 2Text lines produce sharp peaks when they are horizontal, so the angle giving the greatest variation between rows is the true skew.
  3. 3The page is redrawn rotated back by that amount, and the angle found is reported.

What it will not do

  • Corrects up to about eight degrees. A page rotated more than that is not skewed, it is sideways, use Rotate instead.
  • This rasterises the pages, so any text layer is replaced by images. Run it before OCR, not after.
  • Pages that are mostly image with little text give the detector nothing to work with, and are left close to as they were.

Where this runs

Deskew Scanned PDF runs entirely inside this page. Your file is read by the browser, processed in memory and handed back to your downloads folder. It is never sent to a server, because there is no server involved in this tool.

Read the full processing model →