Merge Photos

How it works

Choose the pictures you want to join. They are combined in the order shown in the list, and you can take one out with the cross on its row. Horizontal places them in a row and brings every height down to that of the shortest picture; vertical stacks them in a column and matches every width to the narrowest. That matching only ever scales down — no picture is enlarged past its own resolution and no aspect ratio is distorted. Type a pixel value into the gap field to leave space between the pictures: white space in a JPG, transparent space in a PNG. The output is a single file, and its result line tells you how many pictures went in and how large the finished canvas is.

This tool is also known as merge photos, combine two images into one, side by side photo, stack images vertically, before and after picture.

What is Collage?

A collage is several pictures brought together into one frame, and here it takes its simplest form: a single row or a single column, in the order you chose. Unlike free-layout collage software, nothing overlaps, nothing is tilted and nothing is cropped, which makes the result predictable before you press the button. For comparisons and document pages that is exactly what you want, because the eye follows the pieces left to right or top to bottom without having to work out the arrangement first.

What is Shared edge?

The shared edge is the measurement every piece has to agree on before they can be joined: height when the pictures sit in a row, width when they sit in a column. Without one common value the pieces cannot align and the join leaves uneven steps between them. This tool takes the smallest value present and scales the others down to meet it. It never scales up, because enlarging a low-resolution picture adds no detail at all and only makes that one section look blurred beside sharper neighbours.

Merging into one picture or collecting pages into a PDF?

Merging produces a single picture: the pieces are drawn onto one canvas with no page boundary between them, and the result behaves like any other photo wherever you send it. A PDF keeps the pieces as separate pages, each holding its own dimensions, and gives you a document built for printing. When the point is to see two things at once — a before-and-after, a comparison sent in a chat, a screenshot pair in a bug report — merging is the better fit. For paperwork, multi-page attachments and anything headed for a printer, a PDF is the right container and one page per image is the sensible layout.

Why the shared edge is matched to the smallest picture

Pictures placed in a row need the same height or their bottom edges will not line up, leaving a ragged step where they meet. One edge has to be made common before anything can be joined at all.

That common value is always the smallest one present. The alternative, enlarging, inflates a low-resolution picture artificially and that section looks soft next to its neighbours. Scaling down keeps genuine detail in every piece of the result.

This has a consequence worth planning for: merge a 4000-pixel-tall photo with an 800-pixel screenshot and the entire output is 800 pixels tall. When the large photo's detail is the point, bring the pieces to comparable sizes first, or leave the small one out.

What people use this for

Comparison is the common case: before-and-after shots, two products next to each other, two pages of the same document. As one file it travels as a single attachment through messaging apps and through forms that accept only one image.

The second case is long screenshots. Captured in pieces, they stack back into one page vertically; a few pixels of gap make the seams visible rather than pretending they are not there.

• Before-and-after comparison → horizontal, 10-20 px gap
• Screenshot captured in pieces → vertical, 0 px gap
• Two-page document → vertical, 20 px gap
• Row of logos on transparency → horizontal, PNG output

Check the order and the final dimensions

The merge follows the order of the list. If it is wrong, remove the files with the cross on each row and choose them again in the sequence you want.

Widths add up in a horizontal merge, so several large photos produce a very wide file very quickly. A picture many thousands of pixels across is heavy and some programs struggle to open it at all; bringing the pieces down in size first gives a result you can actually use.

Frequently asked questions

How many pictures can I merge?

There is no fixed ceiling beyond the minimum of two. In practice your device's memory sets the limit, and the output dimensions grow fast once several large photos are involved.

How do I change the order?

The order of the merge is the order of the list. Remove the files with the cross on each row and choose them again in the sequence you want them to appear.

Can I merge pictures of different sizes?

Yes. Heights are matched for a horizontal merge and widths for a vertical one, always to the smallest value present, and every aspect ratio is preserved — nothing is stretched to fit.

Can I pick the colour of the gap?

There is no colour picker. Gaps come out white in a JPG and transparent in a PNG, so choose PNG output when you need the space between pictures to stay see-through.