What Is OCR and How Does It Work?
OCR stands for Optical Character Recognition, and it is the quiet technology behind a huge amount of everyday digital convenience — from searchable scanned books to depositing a cheque by photographing it. Here is what it actually does and why it matters.
The core idea
To a computer, a scanned page or a photo is just a grid of coloured dots. It has no idea that a particular cluster of dark pixels spells the word "invoice." OCR is the process of looking at those pixels and recognising the actual letters and words they represent — turning a picture of text into text you can search, select, and edit.
How it works, step by step
Modern OCR generally moves through a few stages:
- Pre-processing: the image is cleaned up — straightened, sharpened, and converted to high contrast — so characters stand out clearly.
- Detection: the engine locates the regions that contain text and separates them from images and blank space.
- Recognition: each character shape is matched against known letterforms, increasingly using machine-learning models trained on millions of examples.
- Output: the recognised text is reassembled in reading order and saved, often as an invisible layer behind the original image.
Why it is so useful
Once a document has been through OCR, it becomes searchable, its text can be copied instead of retyped, it can be converted to editable formats, and it becomes accessible to screen readers. An archive of scanned paper goes from a pile of pictures to a fully searchable library.
Try it yourself
If you have a scanned PDF that you cannot select text in, run it through the OCR PDF tool to add a searchable text layer — then convert it cleanly to Word or Excel.