What Is Generation Loss?
The reason a photo you keep editing and re-saving slowly turns to mush — a photocopy-of-a-photocopy effect built into how JPG works.
Generation loss is the quality that drains out of a lossy image every time you re-save it. Open a JPG, make an edit, save it again, and the file is re-compressed from scratch — throwing away a little more detail than last time. Do that enough times and the photo visibly degrades, with no way back. It's the digital version of photocopying a photocopy.
Why it happens
JPG is a lossy format: it shrinks files by discarding image detail the encoder judges you won't notice. That's a fine trade the first time. The problem is that the encoder has no memory of the original — each save re-examines whatever pixels it's given and discards again. The second save degrades an already-degraded image; the third degrades that. The losses compound, and because each individual step is nearly invisible, you don't notice until the damage is obvious and the original is long gone.
Where it actually bites
- Editing the same JPG over days. Crop today, adjust brightness tomorrow, add text next week — each session is another save, another generation.
- Re-sharing a shared photo. A picture saved, sent, re-saved and forwarded through a few chat apps can arrive noticeably rougher than it left, because several of those hops re-encode it.
- Screenshotting a screenshot of JPG content, then saving that as JPG again.
What doesn't cause it: simply opening a file and closing it without saving, or viewing it. Loss happens at the re-encode, not the look.
How to avoid it
The rule is one line: keep a lossless master, and export lossy copies from it.
- Do your editing in a lossless format. If you'll work on an image repeatedly, convert it once at the start with JPG to PNG and edit the PNG — PNG is lossless, so you can save it a thousand times and get the same pixels back. Then export a JPG at the very end. (Converting to PNG can't restore what earlier JPG saves already lost — it just stops the bleeding from here on. Our guide on that conversion is clear about the difference.)
- If you must work in JPG, do it in one sitting and save once. One re-encode is fine; it's the repetition that kills.
- Keep the original. Whatever you publish, don't overwrite the source. This is the same discipline that protects your photo's metadata — original stays pristine, the copy goes out.
When you do make that final JPG, choose the quality deliberately rather than letting a tool guess — Compress JPG gives you the control, and our guide on compressing a JPG without artefacts covers where the line sits. Converting a lossy file back and forth between formats to "clean it up" doesn't work either; going back to JPG just adds another generation.
FAQ
Does opening and closing a JPG reduce its quality?
No. Quality is only lost when the file is re-encoded, which happens on save — not on viewing. You can open a JPG as many times as you like.
Does PNG suffer from generation loss?
No. PNG is lossless, so re-saving it doesn't degrade it. That's exactly why it's the format to edit in when a picture will be saved repeatedly.
Can I recover a photo that's already degraded?
Not really — the discarded detail is gone. You can stop further loss by switching to a lossless format, but nothing restores what earlier saves threw away. The lesson is to keep the original next time.