Long Screenshot Stitcher
Took several screenshots while scrolling a chat, article or receipt? Add them in order and this tool finds where each one overlaps the previous one, removes the duplicated rows and repeated top and bottom bars, and saves a single long PNG.
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Fine-tune any seam with the Trim top / Trim bottom fields on each screenshot.
Add screenshots to see the stitched result here.
How to use the Long Screenshot Stitcher
- Add your screenshots: drop them on the box, paste them with Ctrl+V or click Choose screenshots. Each new shot should overlap the previous one a little.
- Check the order: the list runs from the top of the page to the bottom. Use the arrows or Sort by name if your files are numbered.
- Let the tool find the overlaps: each seam shows how many pixels matched and how similar they are. Orange dashed lines mark the seams in the preview.
- Fine-tune if needed: change Trim top or Trim bottom on a screenshot to cut a few more or fewer pixels at a seam.
- Download the stitched image as PNG or JPG, or copy it straight into a chat or document.
How the stitching works
For every pair of neighbouring screenshots the tool compares rows of pixels. First it counts how many rows at the very top and very bottom are identical in both images: those are fixed bars (status bar, app header, toolbar, chat input field) that stay in place while the content scrolls underneath. Then it searches for the offset where the beginning of the scrolling content in the lower screenshot lines up with the content near the end of the upper one. At that offset the upper screenshot is cut (Trim bottom) and the lower one starts below its repeated bar (Trim top). The output height is simply the sum of what is left of each screenshot:
output height = Σ (screenshot height − trim top − trim bottom)
Comparisons use the average brightness of 64 column blocks per row, which is fast enough to check every possible offset and tolerant of small JPEG artefacts. Blank rows carry no information, so the search focuses on rows with visible detail such as text and images.
Reading the seam messages
| Message | What it means | What to do |
|---|---|---|
| Matched N px overlap (99-100% similar) | A clean, exact match | Nothing; the seam is invisible |
| Matched with 97-99% similarity | Match found, small differences (JPEG noise, a changing clock or badge) | Zoom into the dashed seam line and check it reads naturally |
| Repeated top bar / bottom bar N px | Fixed bars detected and shown only once | Nothing, unless a bar should be kept; then lower Trim top |
| No overlap found | The shots do not overlap, are out of order, or the content changed | Fix the order, retake with overlap, or trim by hand |
Tips for great long screenshots
- Scroll by a little less than one screen each time so every shot shares a few lines with the previous one.
- Wait for images and animations to finish loading before each capture; moving content cannot be matched.
- Name files in order (for example shot-1, shot-2…) and use Sort by name, which understands numbers so shot-10 comes after shot-9.
- Choose PNG for chats and documents (sharp text); JPG gives smaller files for photo-heavy pages.
- Many phones and desktop browsers can also take a "scrolling" or "full page" screenshot themselves; this tool helps when that option is missing or cuts off.
Frequently asked questions
How does the automatic overlap detection work?
The tool reduces every pixel row to a compact signature and slides the start of each screenshot along the end of the previous one, looking for the position where the rows match best. Rows that repeat at exactly the same place in both shots, such as a status bar, app header or bottom navigation bar, are recognised as fixed bars and dropped so they appear only once, at the very top and bottom of the result.
What if a seam says no overlap was found?
Then the two screenshots are stacked edge to edge. This happens when the shots do not overlap at all, are in the wrong order, or the page changed between captures (for example an animated banner). Check the order, retake a shot with some overlap, or set Trim top and Trim bottom by hand.
How much overlap should my screenshots have?
A band of about 10-20% of the screen height is ideal. More overlap is fine; less than a few lines of text makes matching less reliable. Avoid scrolling so far that a line of content is skipped between two shots.
Is there a size limit for the long image?
Browsers limit how big a single image can be: about 32,000 pixels tall in most desktop browsers and roughly 16 megapixels in Safari on iPhone and iPad. If the stitched result would exceed that, the tool scales it down to fit and tells you; choosing a smaller output width also helps.
Can I stitch screenshots of different sizes?
Yes. Every screenshot is scaled to the width of the first one in the list before matching, so mixing a slightly cropped shot with full ones works. For the best seams, use screenshots from the same device and zoom level.
Does it work for horizontal panoramas?
No, this tool stitches vertically, top to bottom, which is how scrolling screenshots are taken. To place images side by side without overlap matching, use the Image Combiner.
Are my screenshots uploaded?
No. Matching and stitching run with the Canvas API inside your browser and the result is saved directly to your device, which matters for private chats, bank statements and receipts.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.