Free Image Merger — Combine Images into One

Worked example

Drop three phone screenshots of 1080×2400, 1080×1800 and 1170×2532 pixels. The list shows "3 images" with each size, and the preview reads 1080 × 6537 px. "Layout" starts on "Top to bottom" and "Width" on "Match the smallest", so the third screenshot is scaled to 1080 wide and becomes 2337 tall. Press "Merge 3 images". The page says "Merged: 1080 × 6537 px" followed by the file size, and the download is merged-3-images.jpg, saved as JPG at "Quality" 92%. Now choose "Keep sizes". Nothing is scaled, the canvas becomes 1170 × 6732 px, and an "Align" row appears with "Left", "Centre" and "Right". The two narrower screenshots sit centred, 45 px in from the left, on a "White" background. Back on "Match the smallest", set "Space between" to 20 and "Border" to 40 and the preview reads 1160 × 6657 px.

Which settings to use, and the limits

• Choose the layout and the fit first. "Layout" offers "Top to bottom", "Side by side" and "Grid". The shared measure is "Width" for a column and for grid cells, and "Height" for a row. "Match the smallest" scales every image to the smallest width or height, "Match the largest" scales to the largest, which enlarges the smaller images, and "Keep sizes" scales nothing. Nothing is cropped: every image stays whole.
• Set the grid columns and the alignment. In "Grid", "Columns" offers 2, 3, 4 or 5 and starts on 2. With fewer images than columns, the grid has one column per image. Each row is as tall as its tallest image, and "Align" ("Top", "Middle", "Bottom") places the shorter ones. Four images of 1600×1000, 800×800, 1200×900 and 1000×1000 in 2 columns on "Match the smallest" make a 1600 × 1600 px picture. In a column or a row, "Align" appears only with "Keep sizes".
• Use "Space between" and "Border" for gaps. Both sliders run from 0 to 100 px and start at 0. "Space between" goes between images, and "Border" goes around the outside. They are counted in output pixels, so 20 px is thin on a large image. "Background" fills the gaps: "White" (the default), "Black", "Transparent", or any "Colour" you pick.
• Pick the file format on purpose. "Save as" starts on JPG. JPG and WebP show a "Quality" slider from 50% to 100%, starting at 92%. PNG is lossless and has no slider. JPG cannot be transparent: with "Transparent" the page says "JPG cannot be transparent, so the background will be white. Choose PNG or WebP to keep it transparent." The file is named merged-3-images.jpg, with your image count and the chosen extension.
• Order the images before you merge. Images are placed in list order, numbered 1, 2, 3. Use the up and down buttons ("Move up", "Move down") beside each image, "Reverse order" to flip the list, "Remove" to drop one and "Remove all" to start over. The drop zone now reads "Add more images", and new files go to the end. Photos are drawn upright using their rotation information, so a portrait phone photo does not turn sideways.
• Large merges are scaled down to fit the browser. A merged image cannot be bigger than the browser can draw: 16,384 px on a side at most, and an area limit that depends on the device: 250 million pixels on a desktop, 64 million on Android and 16,777,216 (4096 × 4096) on iPhone and iPad. Over the limit the page says "This is bigger than your browser can make in one image, so it will be scaled down to the size shown." Ten 1080×1920 screenshots stacked would be 1080 × 19200 px, so the result is scaled to 921 × 16368 px.

Common problems and how to fix them

It says "1 file could not be opened as an image." (or "2 files could not be opened as images.")

The browser could not decode that file as a picture, for example because it is damaged or in a format the browser cannot draw. The other files are still added, and only the failed ones are skipped. Export the failed picture as JPG or PNG and add it again. A file of 0 bytes, common with cloud files that were never downloaded, is refused by the drop zone with its own message.

It says "The images could not be merged. Try fewer or smaller images."

Something failed while drawing or saving the result: the browser would not give a 2D canvas, returned no file, or returned a file of a different type from the one you chose. The page checks that the saved type matches JPG, PNG or WebP. Try another "Save as" format, fewer images, or smaller ones, then press the merge button again.

The merged picture is smaller than expected, with the note "This is bigger than your browser can make in one image, so it will be scaled down to the size shown."

The layout is past the canvas limit for your device, so everything is scaled by the same factor. The pixel size beside "Preview" is what will be saved. To keep more pixels, use "Match the smallest" instead of "Match the largest", which enlarges images, merge in two batches, or use a desktop browser, which allows far larger images than a phone.

The merge button is greyed out and the preview says "Add at least one more image to merge."

Merging needs two images or more, and the button stays disabled while only one is in the list. Add another image with the drop zone, which now reads "Add more images". The preview still shows that one image at its own size.

After changing a setting, the download button is replaced by "Merge 3 images" again.

A merged file only counts for the images and options it was made from. Changing the order, layout, fit, spacing, border, background, format or quality makes it out of date, so the page asks you to merge again instead of handing out a file that does not match the preview. The download button reads "Download", or "Save / Share file" on an iPhone.

How it compares

A phone's screenshot stitcher or a photo editor can do more: text, stickers, rounded corners and free placement. This tool does one job. It lays whole images out in a column, a row or a grid, scales them to a shared width or height, adds spacing, a border and a background, and saves one file. It never crops, and it has no text, rotation or free placement, only order and alignment. The size of the result is held to what your browser can draw, which is far lower on an iPhone than on a desktop. In exchange there is nothing to install, and nothing is uploaded: the pictures are joined on a canvas in your browser.