You scanned a page, OCR misread half of it, and now you are wondering whether the format was to blame. It often is. JPG, PNG and PDF each store text-on-a-page very differently, and that choice quietly shapes how accurately an OCR engine can read your document. Pick the right one and you give the recognition step the cleanest possible input.
The short answer
For document text, PNG is the safest single image format because it is lossless and keeps character edges sharp. JPG is fine for clean, high-resolution captures but its compression can smear fine detail. PDF is the best wrapper for multi-page documents, and a PDF can hold either crisp vector text or scanned images inside it. If you are choosing between formats before scanning, lean PNG for individual pages and PDF for anything longer than one sheet.
JPG: convenient, but lossy
JPG is what most phone cameras and many scanners produce by default. It compresses aggressively, which keeps file sizes small, but it does so by discarding detail your eye is unlikely to miss in a holiday photo. The problem is that OCR is not your eye. The faint halos and blocky artefacts JPG introduces around sharp edges land exactly where letters live, and that is where misreads creep in.
JPG is not disqualified. A 300 DPI scan saved at high quality usually reads well. Trouble starts when an image has been saved, screenshotted and re-saved several times, compounding the compression each round. If your source is already a JPG and giving poor results, converting it to a lossless format with JPG to PNG before OCR can recover a little clarity, though it cannot restore detail that compression already threw away.
PNG: the OCR-friendly choice
PNG uses lossless compression, so a black letter stays solidly black and its edges stay crisp no matter how many times you save the file. That edge fidelity is exactly what character recognition depends on. PNG also handles screenshots beautifully, since on-screen text is already pixel-perfect and PNG preserves it without introducing artefacts.
The trade-off is file size: a full-page PNG scan is bigger than the JPG equivalent. For OCR that is a price worth paying. When you pull text out of screenshots in particular, PNG is the format to keep, and our guide to extracting text from a screenshot explains why screen captures OCR so reliably. To explore the resolution side of the equation, see the best image format and resolution for OCR.
PDF: a container, not an image
PDF is the odd one out because it is not strictly an image format at all. It is a wrapper that can hold vector text, embedded fonts, or scanned page images, sometimes all in one file. That flexibility makes it the natural home for multi-page documents.
The catch is that there are two very different kinds of PDF:
- Digital PDFs already contain real, selectable text. OCR is unnecessary; the text can be pulled straight out.
- Scanned PDFs are just pictures of pages stitched together, with no underlying text at all.
If you can highlight a sentence in your PDF, it is digital. If nothing selects, it is a scan and needs OCR. Our walkthrough on making a scanned PDF searchable covers how to add the missing text layer, and how to extract text from a PDF handles both types.
Turning images into one PDF
If you have several page photos, merging them into a single PDF keeps the document together and makes downstream OCR tidier. The Image to PDF tool stitches JPGs and PNGs into one file, and the guide on combining images into a single PDF walks through it.
A practical decision guide
Use this quick logic when capturing documents for text extraction:
- One page, screenshot or screen content? Save as PNG.
- One page, photographed or scanned in good light? High-quality JPG is acceptable; PNG is safer.
- Several pages that belong together? Combine into a PDF.
- Already have a scanned PDF? Run OCR to add a searchable text layer.
- Need an editable document at the end? Send your file through PDF to text or, for a formatted result, see convert a PDF to Word.
Whatever the source format, you can drop the image straight into our image to text tool and let the OCR engine handle the rest.
What matters more than format
Honestly, format choice matters less than resolution and lighting. A blurry PNG reads worse than a sharp JPG. Aim for 300 DPI, even lighting, straight pages and high contrast, and any of the three formats will perform well. Get those basics wrong and no format will save you. For documents full of numeric tables, the structure also matters, and converting PDF tables to Excel preserves rows and columns better than plain text extraction.
Frequently asked questions
Is PNG or JPG better for OCR?
PNG is generally better because it is lossless and keeps letter edges sharp, which is what OCR relies on. JPG can work well at high resolution and quality, but its compression introduces subtle artefacts around text that can cause misreads, especially in files that have been re-saved multiple times.
Should I scan documents as PDF or as images?
Use PDF for anything longer than a single page, because it keeps the document together and is easy to make searchable. For single pages, screenshots or screen content, individual PNG images are simplest. You can always merge images into a PDF later with Image to PDF.
Why does my PDF text not highlight or search?
Because it is a scanned, image-only PDF rather than a digital one. It contains pictures of pages with no underlying text. Run it through OCR to add a text layer, as described in our guide on making a scanned PDF searchable.
Does converting JPG to PNG improve OCR accuracy?
Slightly, in some cases. Converting to PNG stops further compression damage and keeps edges crisp from that point on, but it cannot restore detail the original JPG already discarded. The bigger wins come from scanning at higher resolution and improving lighting and contrast.
Got an image or scan ready? Run it through our free image to text converter and see how clean the extracted text comes out.