Make a signature image
Type your name in a handwriting face or draw it. The PNG comes out with nothing behind the ink.
How it works
A usable signature image is mostly a question of what surrounds the ink. Scan a signature off paper and you get a white rectangle with some dark marks in the middle of it. Drop that onto an agreement and the rectangle hides the signature line, whatever sits beside it, and any text it happens to overlap. The file this page builds carries an alpha channel instead, so the page underneath shows through and the ink sits on the line rather than over it.
What transparent means in a PNG
A PNG stores a fourth number for every pixel: how opaque that pixel is. Zero means nothing is there at all. Everything around the strokes is set to zero, and the soft outer edge of each stroke keeps a partial value, so the signature does not look cut out with scissors. JPEG has no fourth channel. Saving a signature as JPEG forces a background colour to exist, and that colour is the white box that hides the line.
Typed, or drawn
Typing is usually the better option on a laptop. A signature drawn with a trackpad comes out shaky in a way that reads as a forgery rather than as handwriting, and there is no undo for muscle memory you do not have. Draw it when you have a stylus or a phone screen, where your finger traces shapes your hand already knows. Anything on the pad takes priority over the typed name, so clearing the pad brings the typed version back.
Three handwriting faces
The faces are Dancing Script, Great Vibes and Caveat, offered as Flowing, Formal and Casual. Great Vibes is copperplate: fine hairlines, tall loops, the most ceremonial of the three. Caveat is closer to ordinary handwriting with a pen, which suits an initial or a covering note more than a contract. Each one is served from this site under the SIL Open Font License, so nothing about the image you download carries a licensing question with it.
Blue ink is a convention
Signing in blue is a habit inherited from paper. On a photocopy or a fax, blue ink reproduced differently from the black printing around it, so an original could be told apart from a duplicate at a glance. The habit outlived the machines. Black is the right choice when the signature has to match the rest of a printed form. Blue-black sits between the two: a dark navy that reads as a pen without looking like a hyperlink, which is why it is the default.
Size it for the printed line
Width is set in pixels and the height follows the shape of your name, because the image is trimmed to the ink. The default 1200 pixels is four inches at 300 dots per inch, wider than any signature line you are likely to meet. Going much below 600 is a false economy. The file is already tiny, and a signature scaled up later from too few pixels takes on a soft, photocopied edge that no amount of sharpening will remove.
Stroke weight
Weight grows or shrinks the strokes by a number of finished pixels. Great Vibes has hairlines thin enough to vanish when a document is printed at low resolution or pushed through a fax bridge, and one or two pixels of extra weight survives that trip. Negative values thin the strokes, which mostly helps a drawn signature: a trackpad stroke holds one width no matter how fast you move, so it can look heavier than a pen ever would.
Putting it in a document
In Word or Google Docs, insert the PNG and set its text wrapping to behind text, then drag it over the line. In Preview on a Mac, and in most PDF readers, you can paste the image straight onto the page. To place it on a PDF here, take it to Sign a PDF, which opens the document and lets you drag the signature into position on a rendering of the real page.
Questions
How do I check the background is really transparent?
Open the PNG in any image editor. The area around the ink shows as a grey checkerboard rather than as white. In a browser, drag the file onto a coloured page and the colour will show through around the strokes. Turning the transparency toggle off gives you solid white instead, which is occasionally what an older system insists on.
Is a typed name a real signature?
An image of your name applied to a document with the intent to sign counts as a valid electronic signature for ordinary agreements in the US and the EU, and it makes no legal difference whether you drew it or typed it. What you do not get is a certificate-based digital signature: nothing in the file proves who made it. Anything that specifically demands a qualified electronic signature needs a certificate provider instead.
Are the handwriting fonts free to use commercially?
All three are under the SIL Open Font License, which permits commercial use, and the licence text ships next to each file. You are also not embedding a typeface in your document. The PNG is pixels, so no font travels with it and nobody at the other end needs it installed.
Why is the signature not centred in the image?
The image is trimmed to the ink, so there is no empty space for it to be centred in. That is deliberate. When the file is exactly the size of the signature, dragging it onto a line puts the strokes where you dropped them instead of somewhere inside a larger invisible box.
Can I use the drawn signature and the typed name at once?
No, one of them wins. Anything on the pad takes priority, and clearing the pad brings the typed name back. The line under the result names which path produced what you are looking at, along with the ink and the finished pixel size.