Compare & Session History

The bottom of the Editor is the history strip — every stack and edit you’ve made in this session, plus any jobs currently running. The history strip is also the source for the Compare mode, which lets you A/B-evaluate two entries side by side.

Two different “histories”. This page covers the session strip of stacked results along the bottom of the Editor — one thumbnail per stack or opened image, cleared when you quit. It is not the undo system. For per-image undo (⌘Z / Ctrl+Z), the HISTORY timeline panel, and stepping back through edits on a single image, see Edit History.

The history strip

Every time you complete a stack, it lands as a thumbnail at the right end of the strip. Opening a single frame in the Editor — Return, or a double-click on its thumbnail — adds a thumbnail too. The strip scrolls horizontally if you’ve produced more results than fit.

The strip holds up to 25 results per session. Once you cross that limit, the oldest entry drops off the front each time a new result lands — so deleting old work yourself is rarely necessary.

Each thumbnail shows:

The result image — at the resolution that fits the thumb (resizable up to ~100 px).
A caption, on two lines, naming the result:
- For a stack, it’s the name that stack would save as — source folder and date on the first line, the time it was built plus the Look token on the second:
```
bee - 2026-07-30
20.27.04 MS Enh-60
```
  That’s the same text the Save dialog proposes as the default name, minus the extension — so if you accept that default, the caption names the file on disk. Change your file-name pattern and the captions change with it, for the same reason. Two stacks of the same folder are told apart by the time they were built and the Look they carry; change the Look and the caption follows. Save the stack under a name of your own and the caption becomes that name, because from then on that is what the file on disk is called.
  
  A pattern of your own is broken across the two lines wherever it best fits; the split shown above — folder and date above, time and Look below — is the one the standard pattern gets.
- For a single-image edit, it’s the filename of the image you opened.
A caption too long for the thumbnail is shortened from the middle — hover it for the full name.

Active result

The thumbnail with a blue border is the active result — the one shown in the center canvas. Click any thumbnail to switch.

Removing results

Hover any completed thumbnail to reveal a small × in the top-right corner — click it to delete that result from the strip.
Right-click a thumbnail and pick Delete.

The full right-click menu on a completed result is:

Copy file path — puts the result’s path on the clipboard. Only appears when the result actually exists on disk (you saved it this session, or opened it from a file).
Delete — same as the × button.
Send this stack to us… — packages the stack up and sends it to us, for when a result came out wrong and you want us to look at it.

Deleting doesn’t touch any files on disk — it just removes the result from this session’s history. If you haven’t saved the result yet, it’s gone for good once deleted.

In-progress jobs

When you press Stack, the job appears immediately in the history strip with a dim placeholder thumbnail and a green progress bar across the bottom. The progress bar fills as alignment, analysis, and blending proceed.

An in-progress job is captioned like a finished one: the source folder on top, and below it what the stack is currently doing (just Stack until the run reports its first step). The folder line stays put for the whole run, so you can tell several queued jobs apart at a glance. A job started without a source folder shows the status line alone.

Controlling jobs

Hover an in-progress job for an × in the top-right corner — click it to cancel the stack. Useful if you realized you selected the wrong frames and want to start over.
Right-click the in-progress thumbnail and pick Cancel Stack (same effect as the × button).

When a job completes, the placeholder swaps for the real result thumbnail and you can click into it.

Compare mode

The Compare button in the Editor header (or C) puts two history entries side by side. Useful for:

A stacked result vs. one of its source frames — see exactly how much the stack sharpened.
Two stacks of the same subject built from different frame selections — which range captured the antennae better?
Before/after an adjustment-heavy edit — keep the pre-edit result in history and compare against the new version.

Entering compare mode

You need two results in the history strip first. Then:

Click the result you want as A (it’s the currently active one with the blue border).
Click Compare in the header — it’ll prompt you to pick a B if one isn’t selected.

The center canvas splits horizontally into two side-by-side panels with A and B labels in the top-left of each. Each label carries the same caption as that result’s thumbnail — for a stack, the name it would save as, or the name you saved it under — so you can tell which panel is which even when both came from the same folder. Like the thumbnail caption, it shortens from the middle when the panel is too narrow for it; hover for the full name.

Inside compare mode

Pan and zoom are locked together by default (the 🔒 icon shows locked). Scroll on one side, both sides scroll the same way. Pan on one side, both pan together.
Click the lock icon to unlink them — useful for comparing different regions, but most often you want them locked.
Click Swap ⇄ to switch which result is on which side. Visual habit-breaker — sometimes you need to see the comparison reversed to confirm a difference.
The active mask, adjustments, crop, and spot correct all show on whichever side is currently selected (its border turns blue when you click it).

Exiting compare mode

Click Compare again, or press C. The view returns to single-result mode.

Quick before/after on one result

Compare mode is for two different results. To A/B your adjustments on the current result, press \ (backslash) — Lightroom’s Before/After key. It flips the adjustments bypass on and off, the same toggle as the eye icon in the Editor header, so you see the result with and without your Adjustments and masks.

It’s a no-op while you’re in Compare mode or inside a sub-tool editor (Crop, Retouch, Spot Correct, Defringe, or the mask brush) — those own the canvas, so the key is ignored rather than silently changing the hidden result underneath.

Tips

Compare a stack against a single source frame to show — yourself or a client — exactly what stacking bought you.
Keep old results around. The history strip is cheap (just in-memory thumbnails). Don’t delete a result until you’re sure you don’t want to compare against it.
Compare is the fastest way to judge an edit. Keep the pre-edit result as A, apply your adjustments to a copy as B, and flip between them at full zoom to confirm the change actually helped.