In this example, let’s say you want to create a seamless pattern in Adobe Illustrator using vertical stripes. First create a 1:1 artboard at any resolution you like. If you’re creating this for use in 3D, powers of two work best (1024, 2048, 4096, etc). Next, create your first stripe with a solid rectangle, and be sure to turn off the stroke.
Next, ALT+Left Click and drag your rectangle so it snaps to the right edge of your original shape. This is a quick and easy way to copy/paste or duplicate an object, and move it around at the same time. Once you’ve done that, set the fill color for your next stripe. Continue this for as many colors as you want. I’ll do three.
Now, with all of your stripes selected, head up to the Object menu and click Object > Pattern >Make.
Once you click that, you’re brought into a special pattern editing view. From there, you can set specific parameters for your pattern. But by default, it’s seamless. By the way, this pattern (or swatch, as Illustrater calls it) is NOT square, and doesn’t have to be. We’ll get there. When you’re done, click done at the top.
After you click done, you’ll have a brand new swatch in your Swatches panel.
Last step! Turn off your stripe template and grab the rectangle tool and drag it across your entire artboard. Make sure you’re snapping to both corners and holding SHIFT while you drag. Then, set your fill to that fancy new swatch you just made. Done!
Export it at whatever resolution you want, because vectors are cool like that. Hope this helped, hope you learned something new, and you’re rad. See you in the comments!