How to add a signature in Gmail (desktop, mobile and multiple addresses)

Gmail hides the signature setting three clicks deep, strips half of what you paste into it, and then quietly clips the whole thing at the bottom of long threads. None of that is obvious from the settings screen, which is why so many Gmail signatures end up as four lines of grey text nobody reads.

This walks through the setting itself, then the parts that actually decide whether the signature works: pasting HTML that survives, handling multiple sending addresses, and the reply behaviour almost everyone leaves on the wrong default.

Adding a signature in Gmail on desktop

1. Click the gear icon in the top-right corner, then See all settings.
2. Stay on the General tab and scroll down to Signature.
3. Click Create new, name it, and click Create. Name it something you will recognise later — "External" and "Internal" beats "My signature 1".
4. Build or paste the signature into the edit box.
5. Set the two Signature defaults dropdowns underneath.
6. Scroll all the way to the bottom and click Save Changes. Gmail does not autosave this page, and closing the tab discards everything.

That last step is responsible for more "Gmail deleted my signature" complaints than any bug. The save button sits below the fold, past a dozen other settings.

Pasting HTML into Gmail without losing the layout

Gmail's signature box is a rich-text editor, not an HTML editor. There is no source view, no import button, and no way to paste markup as code — paste raw HTML and you get raw HTML, visible in every email you send.

What Gmail accepts is a rendered paste. Open the signature somewhere it displays as a signature, select it with the cursor, copy, and paste into the box. The clipboard carries the rendered HTML and its inline styles, and Gmail keeps most of it.

Most of it, not all of it. Gmail's sanitiser drops anything it does not trust:

• `<style>` blocks and external stylesheets — every style must be inline on the element.
• `class` and `id` hooks, which is the same problem stated differently.
• `position`, `float` in places, and most modern layout CSS. Nested tables with fixed widths still work, which is why serious signatures still use them.
• Images referenced from your hard drive. Only public HTTPS URLs survive.

Build to those constraints and the paste is clean. Build to modern web standards and Gmail quietly rewrites your layout. The full rule set is in email signature best practices, and if the paste worked but the render didn't, the troubleshooting guide covers the usual causes.

If you would rather not hand-build the markup, the BrandSig editor pulls your logo, colours and fonts from your website and puts rendered HTML on the clipboard, ready for this exact paste.

The 10,000 character limit

Gmail caps a signature at roughly 10,000 characters of HTML. A text-only signature never approaches it. A signature with a base64-embedded logo blows past it instantly, because encoding an image as text is enormously wasteful.

If Gmail refuses to save, that limit is usually why. Host the logo at a public URL and reference it with `<img src="https://...">` instead of embedding the data. The signature shrinks by 95%, and the image loads properly for recipients too.

Signature defaults: new emails versus replies

Under the editor sit two dropdowns and a checkbox. They matter more than anything else on the page.

FOR NEW EMAILS USE — the signature on messages you start. Set this one.

ON REPLY/FORWARD USE — separate, and defaults to "No signature". If your signature "only shows up sometimes", this is why. Whether you want it on replies is a real decision: a full signature repeated on every message in a long thread is noise, so many people set a short two-line version here — name and phone — and keep the full one for new messages.

Insert signature before quoted text and remove the "--" line. Tick it. Without it, Gmail buries your signature below the entire quoted thread, where nobody scrolls, and prefixes it with a `--` separator that some clients use to collapse the block out of sight.

Multiple sending addresses

If you send from more than one address — an alias, a second domain, a shared inbox — Gmail lets each one carry its own signature. Above the signature editor there is an address selector; pick the address first, then create the signature for it.

Two things to check when this is set up:

• Under Settings > Accounts and Import, the "Send mail as" list controls which address is used by default and whether replies go out from the address the mail was sent to. A signature attached to the wrong address never appears.
• Gmail applies the signature of the address in the From field at send time, not the one you were looking at when you started typing. Change the From, and the signature swaps with it.

Gmail on iPhone and Android

The mobile apps do not support HTML signatures. There is no workaround: the field is plain text only, on both platforms.

On iOS: Menu > Settings > your account > Signature settings. On Android: Menu > Settings > your account > Mobile Signature.

What you should do is replace "Sent from my iPhone" with something deliberate — name, role, phone number, three lines maximum. It costs nothing and it is the difference between looking mid-conversation-mobile and looking careless.

Note that Gmail on mobile uses the *mobile* signature, not your desktop one, unless you turn the mobile signature off entirely — in which case the desktop signature is used on some account types and nothing at all on others. Test it by sending yourself a message from your phone.

Why yours looks different to the recipient

Gmail on the web renders your signature in the same editor that created it. Your recipient is likely in Outlook, Apple Mail, or Gmail on a phone, and each renders the same markup differently.

Two failure modes account for most of it:

Images blocked by default. Many clients block remote images on first contact. If your name and phone number are inside a picture, they vanish. That is the whole case in HTML vs image signatures — nothing essential should live inside an image.

The signature is too wide. Gmail's compose window is generous; a phone screen is not. Keep the total width at or under about 400px and the layout survives everywhere.

Gmail clips long threads. If a message exceeds roughly 102KB, Gmail truncates it behind a "View entire message" link — and your signature, sitting at the bottom, goes with it. Lean markup keeps you well clear of that.

Checklist before you call it done

• Clicked Save Changes at the bottom of the settings page.
• Both signature dropdowns set, deliberately, including the reply one.
• "Insert signature before quoted text" ticked.
• Logo loaded from a public HTTPS URL, with explicit `width` and `height`.
• Name, title and phone readable with images turned off.
• Every link clicked once, including the logo.
• A mobile signature set on the phone app.
• Test message sent to yourself and opened in Gmail, Outlook and on a phone.

Ninety seconds for the setting. The rest is making sure it arrives intact.

Related reading

• How to add a signature in Outlook (all four versions) — the same job in the client that mangles HTML hardest.
• The professional email signature guide — what belongs in a signature before you paste it anywhere.
• HTML email signature not displaying correctly? Fix it here — diagnostics for when the paste worked and the render didn't.