Best Image Format for Scanned Documents
PDF is the best format for sharing scanned documents, TIFF for archival storage, and PNG for web display. Each format serves a distinct purpose in the document scanning workflow. PDF preserves multi-page documents in a universally viewable container. TIFF provides lossless archival-quality preservation. PNG offers web-compatible display with sharp text rendering.
Scanned documents range from casual receipt captures to legally binding contracts and historical archive materials. The format you choose affects text readability, file size, long-term preservation, and the ability to apply OCR (Optical Character Recognition) for searchable text.
Here is which format to use for different types of scanned documents and scanning contexts.
PDF: The Universal Document Format
PDF is the standard format for sharing scanned documents because it handles multi-page documents in a single file, supports embedded OCR text layers, and displays consistently across every device and operating system. When someone sends you a scanned document, it is almost certainly a PDF.
Modern scanning apps and multi-function printers produce PDF output by default. The PDF can contain the scanned raster image plus an invisible text layer from OCR processing, making the document both visually accurate and text-searchable.
- Multi-page support. A 50-page scanned contract is one PDF file, not 50 separate image files.
- OCR text layer. Invisible text overlay makes scanned documents searchable and copyable.
- Universal compatibility. Every device, operating system, and browser can display PDF files.
- Standard for legal and business documents. Courts, governments, and businesses accept PDF as the standard format.
- Compact compression. PDF supports JBIG2 and JPEG2000 compression for efficient document storage.
TIFF: Archival Quality Scanning
TIFF is the format used by libraries, archives, government agencies, and any institution that needs to preserve scanned documents at the highest possible quality for decades. The Library of Congress uses TIFF for its digitization projects.
TIFF scans preserve every detail of the original document at full scanner resolution, typically 300-600 DPI. Multi-page TIFF files can contain an entire document in one file, similar to PDF. The difference is that TIFF preserves the raw scan data without any lossy compression.
- Lossless quality. Every pixel from the scanner is preserved exactly.
- Multi-page TIFF support. One file can contain multiple scanned pages.
- High bit depth. 16-bit scanning preserves tonal detail in photographs and illustrations within documents.
- Industry standard for archival digitization. Libraries, museums, and government archives use TIFF.
- Large file sizes. The trade-off for lossless quality. A 300 DPI letter-size TIFF is typically 25-75MB per page.
PNG: Web-Ready Document Scans
PNG is the right format when scanned documents need to be displayed on the web or embedded in digital documents. PNG produces sharp, readable text at web resolutions while keeping file sizes reasonable for single-page documents.
For web display, scan at 150-200 DPI rather than the 300+ DPI used for archival. A letter-size page at 150 DPI produces a 1275x1650 pixel PNG, which displays well on screen and typically weighs 200-500KB depending on content complexity.
When JPG Is Acceptable for Scans
JPG is acceptable for casual document scans where archival quality is not important: receipts for expense reports, notes for personal reference, whiteboard captures, and temporary reference copies. JPG produces the smallest files, which is practical for phone-based scanning apps that capture dozens of documents.
However, JPG compression degrades text readability, especially for small print and fine detail. Legal documents, official records, and anything that might need to be reprinted or examined closely should use PNG or TIFF, not JPG.
Scanning Resolution Guide
Scanner resolution (DPI) determines the detail captured from the physical document.
- 150 DPI: Adequate for text-only documents destined for on-screen viewing. Smallest files.
- 200 DPI: Good balance for most business documents. Clear text, reasonable file sizes.
- 300 DPI: The standard for archival scanning, OCR processing, and documents that may need to be reprinted.
- 400 DPI: Recommended for documents with fine detail, small text, or degraded originals.
- 600 DPI: For photographs within documents, fine art, stamps, and currency. Captures maximum detail.
- Color vs Grayscale vs Bitonal: Use color for documents with color content. Grayscale for black-and-white photos. Bitonal (pure black and white) for text-only documents, producing the smallest files.
Converting Between Scan Formats
You may need to convert scanned documents between formats for different purposes. A TIFF archive scan needs to become a PNG for web display. A phone-scanned JPG needs to become a PNG for cleaner text rendering in a presentation.
imageconvert.co can convert scanned document images between TIFF, PNG, and JPG directly in your browser. This is useful for converting legacy scans to modern formats, preparing scans for web publishing, or creating viewing copies from archival originals. All processing happens on your device, so sensitive documents like financial records and legal papers never leave your computer.
Frequently Asked Questions
Should I scan documents as PDF or TIFF?
Use PDF for documents you will share or need searchable text (via OCR). Use TIFF for archival preservation where maximum quality and lossless storage are required. For most business purposes, PDF with OCR is the practical choice.
What DPI should I scan documents at?
300 DPI is the standard for most purposes. Use 200 DPI for quick reference copies and 400-600 DPI for documents with fine detail, small text, or photographs. Higher DPI means larger files and longer scan times.
Can I convert a scanned JPG to make the text clearer?
Converting JPG to PNG or TIFF preserves current quality but cannot recover detail lost during JPG compression. For text-heavy documents, always scan as PNG or TIFF in the first place. If JPG is your only option, use the highest quality setting available.
How do I make a scanned document searchable?
Apply OCR (Optical Character Recognition) to add a searchable text layer. Most scanning software includes OCR. Adobe Acrobat, ABBYY FineReader, and open-source Tesseract all perform OCR. The result is typically saved as a PDF with both the image and text layers.
What format is best for scanning old photographs?
TIFF at 600 DPI for irreplaceable historical photos. The high resolution captures details that may not be visible to the naked eye but could be enhanced digitally. Use 48-bit color (16 bits per channel) if your scanner supports it for maximum tonal range.