Add Outline to Image

How to add an outline to an image

To add an outline to an image, start with a cutout: a PNG or WebP where everything except the subject is transparent. Drop it into the tool above and a stroke is drawn around every edge where solid pixels meet transparent ones. Set the width and colour, add a second outline if you want the layered sticker look, and download the result as a PNG that keeps its transparency, ready to place on a thumbnail.

How the outline is drawn

Many quick methods fake a stroke by stamping copies of the image in a ring around itself, which leaves lumpy corners on thick outlines. This tool measures the true distance from every pixel to the nearest solid pixel of your subject and fills everything within the outline width, so a 40-pixel stroke stays as round and even as a 4-pixel one. The outer edge is anti-aliased, so it does not turn jagged when YouTube scales the thumbnail down.

• Grow the canvas. On by default, so the outline never gets cut off at the edges of the file.
• Leave the bottom edge open. For a person cropped at the chest or waist, this stops the stroke from running along the bottom of the frame, where it would look like a box.
• Second outline. A thin dark line outside a thick white one is the classic thumbnail combination, because it holds up on light and dark backgrounds alike.

What other outline tools get wrong

The tools that rank for this job tend to wrap it in a full editor that wants an account, or send your photo to a server before you see a result. This one does nothing but the outline, and it does it on your device: the image is read with the browser's File API, processed with Canvas and never uploaded. Very large images are scaled to 3,000 pixels on the long side before processing, which is still more than twice the width of a 1280×720 thumbnail.

It does not remove backgrounds. If your photo still has its background, the outline can only frame the rectangle. Read how to remove the background for a YouTube thumbnail for a clean cutout first, then outline it here, add your words with add text to thumbnail and check it at feed size in the thumbnail preview. Or skip the manual steps and generate the whole thumbnail.

Last updated October 24, 2026.