JPG Image Loses Quality Every Time It Is Saved

Why Does JPG Lose Quality When Re-Saved?

JPG (JPEG) is a lossy format. Every time a JPG is saved, the image data is re-encoded — the compression algorithm discards a fraction of the information it deems perceptually insignificant.

The first save loses some data. The second save loses a little more from what remains. The third loses more again. Each generation is slightly worse than the last — this is called generation loss or JPEG generation degradation.

How Bad Is Generation Loss?

It depends entirely on the quality setting used at each save:

Saving at quality 100 repeatedly: Generation loss is nearly zero — each re-save produces almost no additional degradation. Quality 100 is effectively loss-free re-saving.

Saving at quality 85 repeatedly: The first save is the biggest loss. Re-saving the Q85 output again at Q85 adds very little additional degradation — the algorithm has already discarded the data it would discard again.

Saving at different quality levels: Switching between quality levels on re-save causes more degradation than staying at the same level.

The practical rule: One save from a high-quality original to your target quality setting causes most of the visible quality loss. Subsequent re-saves at the same setting add relatively little.

The Real Problem: Opening, Editing, and Re-Saving

The generation loss scenario that actually matters:

1. Start with original (RAW or high-quality TIFF/PNG)
2. Export to JPG for web use ← first quality loss (acceptable)
3. Open that JPG in an editor to make a small change
4. Save as JPG again ← second quality loss (cumulative)
5. Repeat 5–10 times ← visible artefacts build up

How to Prevent Generation Loss

Strategy 1: Always Edit the Original, Not the JPG (Best)

Keep the master copy in a lossless format — RAW, TIFF, or PNG — and only create the JPG as the final export. Never edit the JPG export and re-save it.

Workflow:

• Master: Photoshop .PSD / GIMP .XCF / RAW file
• Edit master → Export to JPG (one step, one quality loss)
• If you need to revise, go back to the master

Strategy 2: Save at Quality 90+ During Intermediate Edits

If you must work with JPGs in a multi-step process, save at quality 90–95 at every intermediate step. This minimises generation loss at each step.

Only reduce quality for the final output.

Strategy 3: Convert to PNG for Active Editing

1. Open JPG to PNG — convert your working JPG to PNG
2. Edit the PNG (lossless — no quality loss per save)
3. Convert back to JPG only for the final output

The Exception: Lossless JPG Operations

Some specific operations can be performed on a JPG without any quality loss:

• Rotation in multiples of 90° (using a lossless-rotate-capable tool)
• Cropping to certain dimensions (using lossless crop tools)

Most photo managers (Windows Photo, macOS Photos, Google Photos) automatically use lossless rotation. Saving in Photoshop, GIMP, or most editing software will re-encode the full image.

Frequently asked questions