Notes · Develop

Why is my Lightroom Classic export so slow?

If an export or publish crawls, the time is almost never spent writing the file. It's spent rendering your edits — and some edits are far more expensive than others.

Where the time goes

Lightroom Classic stores edits as instructions, not pixels. Every export re-applies them to the full-resolution raw file. Sliders are cheap. These are not:

AI masks (Subject, Sky, People, Objects) — recomputed at full resolution on export.
Lens Blur — a depth map plus a blur, per photo.
Denoise and other AI enhancements — slow the first time; if they create a new DNG, export that one.
Generative Remove and heavy healing — many spots add up.

A 50-megapixel photo with a few AI masks can take many times longer than one with only basic adjustments. Publishing through any service — including our plug-ins — pays the same rendering cost.

What helps

Use the graphics processor for export. In Settings › Performance, set the graphics processor to Auto or Custom and make sure it's also used for export, if your version offers it. This often makes the biggest difference on Apple silicon.
Export smaller. Rendering scales with output size. For screens, about 6000 pixels on the long side is plenty.
Run exports side by side. Lightroom Classic can run more than one export at a time; two batches together usually finish sooner than one after the other.
Keep the catalog and previews on a fast internal drive, and leave the Mac awake and plugged in for long batches.

Our plug-ins log how long Lightroom Classic spent rendering each photo versus what the plug-in itself did, so you can see where a slow publish actually spent its time.