How to use it
Drop a screenshot on the page, paste one with ⌘V or Ctrl+V, or press Choose a file.
Pick a tool from the bar, or press its key: A for an arrow, R for a box, T for a note, S for a numbered step, H for a highlight, P to draw freehand. Drag on the picture to draw, or click to place a note or a step.
Pick a colour and a line width. To change a mark later, press V, click the mark, then drag it, recolour it or delete it.
Press Download PNG, or Copy to paste it straight into a message.
Doing it well
One arrow for one point. If you need three arrows, number the points with steps instead. 1, 2, 3 reads in order, and three arrows don't.
Keep a note to a line. If it needs a paragraph, it belongs in the message around the picture.
Use the highlight on one line of text. Spread over a whole block, it stops telling the reader where to look.
Freehand is for a quick circle or an underline. For anything that has to look neat, use an arrow or a box.
Dragging moves a mark. It doesn't resize it. If an arrow is the wrong length, delete it and draw it again, which takes a second.
Do the other jobs first. If the screenshot has anything private in it, cover it with a solid block before you mark it up. If you want it on a gradient for a post, add a backdrop last.
The same tools, the moment you capture
VizShot's editor has these six tools on the same keys the moment you take the screenshot, with more including Crop, and your marks stay movable until you save. Mark up a screenshot lists every tool, and you can download VizShot and try it free for 14 days.
Questions
Is my picture uploaded?
No. The picture is opened, marked up and saved inside your browser, and no request carries it anywhere. Your browser's network panel will show you if you want to check.
Can I move a mark after I place it?
Yes, for as long as the page is open. Press V, click the mark, and drag it, or move it with the arrow keys. You can recolour it or delete it too. Dragging moves a mark and doesn't resize it. To change the size, delete it and draw it again.
How do I number the steps in a screenshot?
Press S, then click where each number should go. They count 1, 2, 3 as you click. If you delete one, the others keep their numbers, and the next badge is one more than the highest number on the picture.
Can I draw freehand on the picture?
Yes. Press P and drag, or draw with a finger on a phone. The line is one mark, so you can move it afterwards.
Is this a full image editor?
No. It has six tools for marking up a screenshot, and it doesn't crop, resize, filter or retouch. VizShot's editor has more tools, Crop among them.
What file do I get?
A PNG with the same width and height as the picture you dropped in, with the marks drawn on it at full size. In the file the marks are part of the picture and can't be moved. The page keeps your marks until you leave it, so you can change them and download again. The three-step version with an app is on the annotate a screenshot page.