A scanned signature that still has its paper around it is only half done. The useful artifact is the ink alone — a transparent PNG you can drop onto any document without a white rectangle glued to it. Here’s the whole pipeline, and where each step goes wrong.

Get a clean capture first

Background removal can only delete what the capture separates cleanly, so ninety percent of the result is decided before you open a tool.

• Paper: plain white, unlined, matte. Cream or textured paper compresses into the same colors as ink edges. Avoid graph paper — every ruled line becomes part of the cleanup.
• Ink: a dark pen — black or dark blue gel/fineliner, medium tip. Ballpoints skip and leave grey streaks that sit uncomfortably close to paper white in color space.
• Light: even and diffuse, no shadows of your hand or phone across the sheet. A desk lamp off to the side plus daylight works; a single overhead light with your phone in the way doesn’t.
• Resolution: scan at 300 dpi or higher if you have a scanner. From a phone, fill the frame with the signature and aim for at least 2000 px on the long edge — thin strokes need pixels to survive cleanup.
• Sign several times on one sheet and pick the best; it’s free.

Why color mode beats AI for ink

Signatures are the textbook case where the dumb algorithm wins. Ink on white paper is a high-contrast, hard-edged subject: every pixel is either clearly ink or clearly paper, with a thin anti-aliased transition in between. A color-range removal keys on exactly that difference and produces a crisp binary edge.

The AI mode is built for a different problem — finding the object in a photo of a cluttered scene. It estimates a soft matte at 320×320 and upscales, which is exactly what you want for hair or a person on a beach, and exactly wrong for 0.5 mm pen strokes: fine lines get interpreted, softened, and occasionally broken. For signatures, pick color mode — no download, and a truer edge.

Remove the paper

1. Drop the scan or photo into the tool on the home page. The default Connected background mode auto-removes the dominant border color — on a scan that’s already the paper.
2. If the scan was cropped tight (paper doesn’t reach all four edges), switch Remove to Same color everywhere, or click on the paper itself to re-seed.
3. Now tune Tolerance — this is the one setting that decides quality:
   • Too low: paper texture, JPEG noise and scanner dust survive as confetti around the strokes.
   • Too high: the light grey anti-aliased pixels on stroke edges get eaten — thin lines break, and the inner loops of a, e, o fill in.
   • Practical range on a decent scan is roughly 15–30. Raise it in small steps and watch a thin stroke at maximum zoom; stop the moment the paper noise is gone and the stroke edges still look continuous.
4. Leave Edge feather at 0–1 px for print use; a pixel of feather smooths screen display but eats hairline strokes.
5. Download the PNG — always PNG, never JPEG (JPEG has no alpha; the paper would bake back in as a solid fill).

Where to put it

• PDF: in Acrobat use Fill & Sign → Add signature → Add image. In Preview on macOS there’s no file-import for signatures — instead open the PNG, copy it (Edit → Copy), and paste it onto the open PDF: it lands as a movable object with transparency preserved. Both render the signature over the page.
• Word: Insert → Pictures, then set Wrap Text → In Front of Text so the signature can sit on the signature line instead of pushing text around.
• Google Docs: Insert → Image → Upload, then set text wrapping to In front of text the same way. For repeated use, keep the PNG in Drive.
• Email signatures: place it in your mail client’s signature editor. Caveat: most clients want a hosted image URL or inline attachment; a pasted PNG usually works, but test by sending to a second account — some clients re-encode to JPEG and the background returns.

Two pitfalls worth knowing

Dark mode. A black signature is invisible over a dark UI theme or a dark letterhead. If the destination is a digital context that may render dark — email clients, app dashboards, dark-themed docs — export a second variant: re-run the removal, set New background to transparent still, but first invert or lighten the ink, or composite the signature on white and keep both files. The safe pair is signature-black.png and signature-white.png.

JPEG anywhere in the chain. Screenshotting the result, pasting through a clipboard that flattens alpha, or letting a service “optimize” the upload can silently strip transparency. If the PNG suddenly shows a white box, the alpha was flattened somewhere — re-export from the original removal, don’t patch the flattened file.

Keep the original scan. Background removal is destructive in one direction — you can always re-cut the paper, but you can’t recover a stroke edge that an aggressive tolerance ate.

Frequently asked questions

Why not just crop the signature photo instead of removing the background?

A crop keeps the white paper as an opaque rectangle — it works on a white page but leaves a visible box over letterhead, shaded table cells, certificates or dark themes. Removing the paper makes the ink float: it can sit over a signature line, a logo block or a colored letterhead without a white patch around it.

My signature is ballpoint blue — which mode should I use?

Color mode, either way. Dark blue or black ink on white paper is a high-contrast, hard-edged subject — exactly what a color-range or flood fill removes cleanly. The AI mode is built for photos of objects on busy backgrounds; on a flat scan it adds a download and a soft matte you don't need.

Can I save the result as JPEG?

No — JPEG has no alpha channel, so saving as JPEG flattens the transparent paper area to a solid color and you're back to a white box. Always export PNG (or WebP, if every target app supports it). If a destination insists on JPEG, fill the background white instead of transparent.

Is a scanned transparent signature legally valid?

That's a jurisdiction and context question, not a technical one. Many routine documents accept inserted signature images (invoices, internal approvals, some contracts); notarized documents, wet-ink requirements and e-signature statutes differ by country. When in doubt, use a proper e-sign service or wet ink — the image file itself is never the legally sensitive part; the signing process is.