About the Line Tool
Draw straight lines and arrows on a picture to point at things: an arrow to a button, a line that connects two parts of a diagram, a pointer in a photo of a product. Drag from the start to the end, and switch on the arrowhead if you want one. Choose the colour and thickness, snap lines to 45 degree angles for neat horizontals and verticals, draw as many as you like, undo the last one and save a full-size PNG. Your picture is edited in your browser and is never uploaded.
Updated October 2026
How to use the Line Tool
- 1Select an image or drop one on the page.
- 2Choose a colour and thickness, and switch the arrowhead on if you want an arrow.
- 3Drag on the picture from the start of the line to its end.
- 4Switch on Snap to 45° angles for perfectly horizontal, vertical or diagonal lines.
- 5Press Undo to remove the last line and Download PNG to save.
Lines and arrows as annotation
Arrows are the clearest way to direct attention: this button, that error, this part of the product. Plain lines connect and measure: they join a label to its object, mark a distance on a plan or underline a word. Both are quicker than describing a position in words.
Straight and tidy
Hand-drawn lines wobble. Snap to 45° angles removes the wobble by locking the line to horizontal, vertical or diagonal. Use it for underlines, frames and tidy pointers, and leave it off when an arrow must point at a specific object at an odd angle.
- Underline: snap on, horizontal drag
- Pointer: snap off, any angle
- Connect two labels: snap off for the exact line
Thickness and head size
Thickness is in picture pixels and scales with the picture. The arrowhead grows with the thickness, so a thicker arrow has a larger head. For a big photo, raise the thickness so the arrow is visible when the photo is shown small.
A quick example
Take a screenshot of a settings page. Choose red, thickness 5 and switch the arrowhead on. Drag from empty space toward the toggle you want people to change. Add a second arrow to the save button. Download the PNG and paste it into your instructions.
Arrows that people follow
Start an arrow in empty space and end it right at the target, so the head touches the detail without covering it. Use one colour for the arrows in a set of instructions and number steps with Add Text to Image if the order matters. Keep arrows short; a long arrow crossing the whole picture is hard to follow. Check the result at the size people will see it, since a thin arrow on a large photo can vanish when it is shown small.
Phone and computer
On a phone, drag with one finger; the page does not scroll while you touch the picture. On a computer, hold Shift to snap. The picture is saved at its full size.
Good to know
Lines are part of the saved PNG and cannot be removed afterwards, so keep your original file. For text labels use Add Text to Image; for boxes, Rectangle Tool; for circles, Ellipse Tool.
Features
- Straight lines and arrows
- Adjustable colour and thickness
- Snap to 45 degree angles
- Undo and Clear all
- Touch, mouse and pen supported
- Private: runs in your browser
Frequently asked questions
How do I draw an arrow?
Switch Arrowhead to Yes. The arrowhead is drawn at the end where you lift your finger or mouse button.
How do I draw a perfectly straight line?
Switch Snap to 45° angles on, or hold Shift while you drag on a computer. The line snaps to the nearest multiple of 45 degrees.
Can I make a dashed line?
Not yet. Lines are solid.
Can I move or edit a line after drawing it?
Not yet. Press Undo to remove the last line and draw it again.
Which colour is best?
Red and yellow stand out on most pictures. Use white on dark pictures and black on light ones.
Is my picture uploaded?
No. Everything stays in your browser.