Merge Images

A great many places accept exactly one image. Marketplace listings, forum posts, review forms, bug trackers, chat messages and most social platforms all have a slot rather than a gallery, and the usual workaround — posting several images in sequence — means the viewer has to remember the first one while looking at the third.

Merging solves that by putting the comparison inside a single frame. A before-and-after sits side by side where the difference is immediately visible; three product angles arrive together; a sequence of screenshots reads as one story. Nothing has to be clicked through.

It is also the simplest way to make a comparison honest. Two images shown together at the same scale are much harder to misrepresent than two images shown one after another.

Horizontal merging puts images side by side, which is the natural choice for comparisons. The eye moves across easily and the two halves are read as a pair. This is the standard layout for before-and-after edits, product variants and any A-versus-B.

Vertical merging stacks images down the page. It suits sequences and instructions, where the order matters and top-to-bottom implies progression. It is also the better choice for anything that will be viewed on a phone: a tall image fills a portrait screen, whereas a wide one gets scaled down until the detail disappears.

If you are unsure, ask what the viewer is meant to do. Comparing? Go horizontal. Following? Go vertical.

Images of different dimensions are aligned on the joining edge and the remaining space is filled with your background colour. That is a reasonable default, but the result looks noticeably tidier when the images share a dimension — a common width for a vertical stack, a common height for a horizontal strip. Running them through the Resize tool first takes a moment and improves the outcome considerably.

A gap between images is worth adding more often than not. Without one, two photographs with similar edges can appear to be a single continuous scene, which is confusing at best and misleading at worst in a before-and-after. Ten to twenty pixels is usually enough to signal the boundary without looking like a collage.

The background colour fills both the gaps and any leftover space. White suits most contexts; a mid-grey often looks better behind photographs, and matching your brand colour works well for anything being published.

In the automatic layouts, with Image sizes left on Original, the images are drawn at their native pixel dimensions. No resampling happens and nothing is softened, so the merged result is exactly as sharp as its inputs. That is the mode to use for stitching screenshots, where a half-pixel of softening on text is immediately visible.

Scaling is what costs you. Resizing an image on the Custom canvas, or choosing Match or Fill so everything shares a size, resamples that image — unavoidable, and no worse than any other resize, but worth knowing when the alternative was free.

The only quality consideration is the export format. Choose PNG or WEBP to keep everything exact, or JPG if the result is a photograph and you want a smaller file. If the merge contains screenshots or text, PNG is clearly the better choice — JPG's artefacts cluster around exactly the sharp edges that lettering is made of.