By Rémy Boiré · Updated
How to use the seamless pattern checker
Bring in your tile
Drop a PNG, JPEG or WebP on the preview, paste it, or open it from your files. From Procreate on iPad, export the canvas as a PNG (Actions, Share, PNG), save it to Files, then open it here in Safari.
Pick the repeat
Grid, Half-drop or Brick. When your tile only works in one of them, the checker opens on that one, and the result says which repeats it fits.
Read the result
Orange marks sit where the edges don’t meet. Under the preview, the result says what’s wrong in plain words, and the close-ups show the pixels on both sides of each seam, enlarged six times.
What the checker looks for
The four problems Seamply’s checker flags. Causes and fixes come from Seamply’s hairline guide, checked against Procreate, Adobe and Spoonflower documentation on September 25, 2026.
| Problem | What you see in the repeat | Usual cause | Fix |
|---|---|---|---|
| Edges that don’t meet | A shape stops at one edge and doesn’t come back on the other side, or comes back shifted | Something was drawn across the edge without offsetting the tile, or moved afterwards | Offset the tile and paint across the seam |
| A 1-pixel line along an edge | A thin pale or dark line between tiles | A layer moved or resized between two pixels, or an export at another size | Move with Nearest Neighbor interpolation, and export at 100% of the canvas |
| Partly transparent edge | A pale line, only over a colored background | Soft pixels where a stroke was cut by the canvas edge | Paint the edge until it’s fully opaque |
| Odd width or height | Steps or a soft line along half-drop or brick seams | Half of an odd number of pixels falls on half a pixel | Use even dimensions, such as 3000 × 3000 px |
Sources: Procreate Handbook, Interpolation, Adobe Community, thin line after resizing, Adobe Community, white hairlines in a repeat pattern, Spoonflower, checking for repeat flaws. Checked on .
How it decides: for each pixel along an edge, the checker compares the jump to the pixel on the other side of the seam with the change just inside the tile. A seam is a jump much bigger than what surrounds it, over several pixels in a row. Grain and texture change a lot everywhere, so they don’t count as seams. The edges are always read at full size, even when the preview of a large image is scaled down.
Grid, half-drop and brick
How each repeat places the tile, as Seamply’s checker draws it, with the names Spoonflower uses, read in Spoonflower’s help center on September 25, 2026.
| Repeat | How the tiles are placed | Must be even | Spoonflower calls it |
|---|---|---|---|
| Grid | Side by side, in rows and columns | Nothing | Basic |
| Half-drop | Every other column moves down by half the tile’s height | The height | Half-Drop |
| Brick | Every other row moves across by half the tile’s width | The width | Half-Brick |
Sources: Spoonflower, Repeat Options. Checked on .
A tile can fit one repeat and not another: a half-drop tile shows seams as a grid. That’s why the result lists all three. Turn a half-drop a quarter turn and it becomes a brick, so check the tile the way it will be printed.
Your image stays on your device
The checker opens your image in the browser, on your device, and never sends it anywhere. You can try it: load the page, turn off Wi-Fi, then drop an image. It still works.
The site counts page visits without cookies, and nothing about your image: not its name, not its size, not its pixels. The details are on the privacy page.
Limits
- Flat images only: PNG, JPEG, WebP, and whatever else your browser can open. A PSD has to be exported as a PNG or a JPEG first.
- Up to 16,384 pixels on a side. A very large image can still be too much for the browser’s memory, on an iPad especially; the checker then says so.
- Past 2,048 pixels, the preview is scaled down. The edges are still checked at full size.
- It checks the file, not the print: the color, the paper and the scale are up to your printer. For sizes, see canvas size for seamless patterns.
- It shows the seams but doesn’t fix them. How to check a seamless pattern and fix hairline seams goes through each cause.
Keep your layers
This checker reads a flattened copy of your work, so every fix means a new export. Seamply does it on the iPad, with your layers.
Questions
Is this seamless pattern checker free, and is my image uploaded?
It’s free, with no account. Your image is opened in your browser and never sent anywhere; once the page has loaded, the checker works offline.
How do I check a Procreate pattern on iPad?
In Procreate, export the canvas as a PNG (Actions, Share, PNG) and save it to Files. Open this page in Safari, tap Open an image and pick the file. The checker reads flat images, not PSD files.
What’s the difference between a grid, a half-drop and a brick repeat?
In a grid, the tiles sit side by side. In a half-drop, every other column slides down by half a tile; in a brick, every other row slides across by half a tile. Spoonflower calls them Basic, Half-Drop and Half-Brick.
Does the checker work for textures?
Yes, for any image meant to tile: a game texture, a background, a paper. It checks that the edges meet; it doesn’t judge whether a repeated texture looks too regular.
Can the checker fix the seams it finds?
No, it only checks. The reliable fix is to bring the seam into the middle of the tile and paint over it, as explained in how to fix hairline seams. Seamply does that offset on the iPad and keeps your layers.