How to Merge Images Side by Side Without Losing Quality
Which layout to pick, why mismatched heights leave an ugly seam, and the spacing and format settings that keep a combined photo sharp.
Two photos, one file. It sounds like the simplest edit anyone could ask for, and usually it is — right up until the two pictures turn out to be different heights and the result looks like a ransom note.
Most of the frustration with combining images comes down to three settings nobody explains: how the sizes get reconciled, how much gap sits between the pictures, and what fills the space that’s left over. Get those right and the rest is a download button. The Merge Images tool does all of it in the browser, with nothing uploaded.
Pick the layout from the job, not the look
Side by side is for comparison. Before and after, two paint samples, the same room from two angles — your eye reads left-to-right and compares, which is exactly what you want.
Stacked is for sequences. A long chat thread split across three screenshots, a receipt photographed in two halves, step-by-step instructions. Stack them and the thing reads top to bottom like a single tall page.
Grid is for sets where no single picture is the point: four product shots, a mood board, nine frames from one shoot. Two columns of two reads cleanly. Three across starts to feel like a contact sheet, which is fine if that’s the intent.
Mismatched heights are what ruins it
Here’s the part that trips people up. An iPhone screenshot is 1290 × 2796. A photo from that same phone’s camera is 4032 × 3024. Drop both into a side-by-side merge at their original sizes and the canvas comes out 5322 × 3024 — tall enough for the photo, with 114 px of dead background above and below the screenshot. It looks like a mistake, because it is one.
Switch the sizing control to match the smallest and the photo gets scaled to 3728 × 2796. Now both pictures are exactly 2796 px tall, the edges line up flush, and there’s no leftover background to explain away.
Matching to the largest works too, and the trade is obvious once you say it out loud: the screenshot would be stretched from 2796 up to 3024 px, gaining 8% in size and nothing in detail. Enlarging invents pixels. Shrinking just throws some away, which the eye forgives far more easily. When in doubt, match down.
Keep original sizes earns its place when your inputs already agree — two frames from the same camera, two crops you made at the same dimensions. Then nothing is resampled at all and every pixel survives the trip.
Gap zero is a real setting
If you’re reassembling something that was split — a screenshot cut in two, the halves of a panorama — set both the gap and the border to 0. The pictures touch edge to edge and no background pixel appears anywhere in the output. People often leave the default gap in place and then wonder why there’s a hairline running through their panorama.
When you do want a gap, decide on the colour deliberately. White works on a white page and looks like a bug on a dark one. For PNG and WebP you can tick Transparent instead and let whatever sits behind the image show through.
PNG for edges, JPG for photographs
Two screenshots merged and saved as PNG stay pixel-exact: the text is as crisp as it was. The same pair as JPG picks up faint grey halos around the letters, which is JPEG doing what JPEG does to hard edges.
Photographs flip the calculation. A merged pair of camera shots might be 14 MB as PNG and 1.4 MB as JPG at quality 92, and you would struggle to tell them apart side by side. WebP typically undercuts both by another 20–30% and keeps transparency, which is worth remembering.
One ceiling to know about
Browsers won’t allocate an arbitrarily large canvas. Six 4032 × 3024 photos in a single row would need 24,192 px of width and 73 megapixels of memory, so the tool caps the output at 12,000 px per side and about 60 megapixels, then shrinks the whole collage proportionally when you cross the line. The status row tells you when that happened. Reshaping into a grid fixes the per-side limit but not the total area: four of those photos as a 2 × 2 grid comes to 8064 × 6048, or 49 MP, and fits fine, while six won’t whatever shape you pour them into. Merge in pairs and combine the results if you need every last pixel.
Add your pictures to the Merge Images tool, set the layout, and check the preview — it’s the actual output canvas, so what you see is what downloads.