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How to add an HTML signature in Gmail

Gmail accepts formatted signatures but pastes them through a filter. Here is the exact sequence, plus the three limits that catch people out.

The steps

1. Open Gmail on a desktop browser. The mobile app cannot install an HTML signature — this has to be done once on desktop, after which it applies to mail sent from the web client.
2. Click the gear icon, then See all settings.
3. Stay on the General tab and scroll down to Signature.
4. Click Create new, name it, and click Create.
5. Click inside the signature box and paste with Ctrl + V (or Cmd + V). Paste the rendered signature, not the HTML source — Gmail's box is a visual editor and will show raw code as text.
6. Underneath, set For new emails use and On reply/forward use. Leaving the second one blank means replies go out unsigned.
7. Scroll to the bottom of the page and click Save Changes. Nothing is saved until you do.

The three limits worth knowing

10,000 characters

Gmail caps a signature at 10,000 characters of HTML. A text-and-logo signature is well under a thousand, so this only bites when someone pastes a signature exported from a design tool, where a single layout can run to tens of thousands of characters of markup.

Gmail rewrites some of your CSS

Gmail keeps inline styles but discards anything it considers unsafe or unnecessary: position, @media queries, classes referencing stylesheets that no longer exist. Table layout with inline styles survives; a signature built with modern CSS loses its layout.

The trimming arrows

Gmail hides repeated content behind the "…" button, and long signatures in a thread often end up collapsed. Keeping the signature short is the only real fix — and it is the right call anyway.

Why the logo does not appear

Usually one of three reasons, in order of frequency:

• The image is not public. A Google Drive share link is not an image URL. The address has to end in the image file itself and be openable in a private browsing window.
• The recipient has images blocked. Nothing you can do, which is the argument for never putting information inside an image.
• Mixed content. An http:// image on an https:// page is often blocked. Use https://.

Gmail on iPhone and Android

The Gmail app has its own plain-text signature setting, separate from the web one, and it does not support HTML. Mail sent from the app uses the mobile signature; mail sent from the browser uses the HTML one. Keeping the mobile version to name, role and phone is the least jarring approach.

Aliases and "send mail as"

If you send from more than one address in one Gmail account — an alias, or another mailbox added under Send mail as — signatures are chosen per address, not per account. Gmail picks the default signature for whichever address is in the From field, and switching the From field mid-compose can silently swap the signature underneath you.

Two consequences worth knowing. First, adding a new alias does not give it a signature: until you set one, mail from that address goes out bare. Second, if a message ever goes out with the wrong signature, the cause is almost always that the From address was not the one you assumed.

Where the signature sits relative to quoted text

Gmail has a setting most people never touch that decides whether your signature is placed above or below the quoted text of the message you are replying to. Above is the default and is what nearly everyone expects; below is technically more correct in traditional email etiquette and looks wrong to most modern readers.

The practical reason to know about it: if your signature keeps ending up at the very bottom of a long thread where nobody sees it, this setting is why.

Confidential mode and other Gmail features that drop it

A few Gmail paths bypass your signature entirely, and it is worth recognising them rather than debugging them:

• Confidential mode sends the body through a hosted view; formatting and signatures are not treated the way a normal message is.
• Templates (formerly canned responses) may include a signature captured when the template was saved, which then goes stale when you change the real one.
• Scheduled send keeps whatever was in the compose window, so a signature changed afterwards does not apply retroactively.
• Plain text mode in the compose menu removes the HTML signature and substitutes nothing.

A two-signature setup that works

The arrangement most people converge on after a while, and worth adopting directly:

New messages:  full signature — name, role, company, one link
Replies:       one line — name and phone

The reasoning is that a new message often goes to somebody who does not know you, where the signature is doing identification work. Inside a thread they already know, and a repeated block of five lines in a twelve-message exchange is what makes Gmail collapse the thread behind the trimming arrows.

Both are set in the same place, in the two dropdowns under the signature editor. It takes one extra minute and it is the single change that makes a signature feel considered rather than automatic.

Multiple signatures

Gmail supports several signatures and lets you pick per message from the pen icon in the compose window. Useful if you write in more than one language, or work under two brands — generate one signature per case with the same layout and different details.

Frequently asked questions