What is the most common mistake people make when they save scans as JPEGs for long-term keeping?

The single biggest mistake: treating JPEG as a preservation format

The most common mistake is using JPEG as the master (preservation) copy of a scan. JPEG was designed to make photographs small for sharing and display, not to keep records intact for years or decades. The problem is lossy compression: every time JPEG saves an image, it permanently discards picture data to shrink the file. That data never comes back.

This causes two related issues:

• Permanent quality loss. Fine detail, faint text, and subtle tones are thrown away at the moment of capture. You cannot “restore” them later.
• Generation loss. Each time someone opens a JPEG, edits it (rotates, crops, annotates), and re-saves, the file is recompressed and degrades further. After several rounds, a scanned document can become noticeably blurry or blocky.

For records you must keep and trust over time, that degradation is a real risk to authenticity and readability.

What good practice looks like instead

Widely used digitization guidance recommends capturing a high-quality master in a format suited to preservation, then deriving smaller copies for everyday use.

• Capture a preservation master in an uncompressed or losslessly compressed format such as TIFF (or PDF/A for documents). This is the file you protect and rarely touch.
• Create access derivatives from that master. JPEG is perfectly fine here — for web viewing, email, or quick reference.
• Scan at adequate resolution and bit depth the first time. You cannot add detail later by rescaling a JPEG.
• Don’t repeatedly edit and re-save JPEGs. Make changes from the master and export a fresh derivative.
• Capture and keep metadata (date, source, device, settings) so the digitized record stays identifiable and verifiable.

The takeaway

JPEG is a delivery format, not an archival one. Keeping only JPEGs means you have only the compressed, lossy version of your record — with no full-quality original to fall back on. Save a robust master, and let JPEG do what it does well: easy sharing.

For more on capture standards and file-format choices, see the digitization and imaging topic hub.