HTML Email Signatures in Gmail: What Works and What Breaks

By Patronum

November 13, 2026

Read Time: 6 mins

HTML Email Signatures in Gmail: What Works and What Breaks image

How do you add an HTML signature to Gmail?
A starting-point HTML skeleton
Which HTML and CSS hold up when the email arrives?
Is there a character limit for Gmail signatures?
What happens to an HTML signature in dark mode?
How does Outlook show a signature sent from Gmail?
How Patronum handles HTML signatures
FAQ
Sources

Gmail’s signature settings give you a formatted text box, not an HTML code view. So an HTML signature gets into Gmail one of two ways: you paste the rendered signature into the box, or an admin sets the HTML through the Gmail API. Build it with tables, inline styles and hosted PNG or JPG images.

How do you add an HTML signature to Gmail?

Paste the rendered version, or use the API. Google’s steps describe typing your signature into a box and formatting it with images and text styles (Gmail Help). There’s no source button, so raw code pasted into the box shows up as text.

For one person (paste the rendered signature):

Open your HTML file in Chrome or another browser, so you see the finished signature, not the code.
Select the whole signature and copy it.
In Gmail, click Settings > See all settings, scroll to Signature, and pick or create a signature.
Paste into the box, then click Save Changes at the bottom of the page.
Send a test to an outside Gmail address and an Outlook address.

For a whole company (the Gmail API): each send-as address has a signature field that holds an optional HTML signature for messages composed in Gmail on the web, and it’s added to new emails only (Gmail API reference). Writing it needs the gmail.settings.basic or gmail.settings.sharing scope (sendAs.patch). Google’s admin help calls this route one for advanced users and notes that users can still edit the result (Google Workspace Admin Help).

The Admin console’s Append footer isn’t an HTML route, because its editor doesn’t accept HTML content (Google Workspace Admin Help). Our guide to setting a signature for all users compares the admin routes.

A starting-point HTML skeleton

Treat this as a base to adapt and test, not a proven template: one table, inline styles, a hosted PNG with width, height and alt text, and a common font stack.

<table cellpadding="0" cellspacing="0" border="0" role="presentation" style="border-collapse:collapse;font-family:Arial,Helvetica,sans-serif;font-size:13px;line-height:18px;color:#333333;">
  <tr>
    <td style="padding:0 12px 0 0;vertical-align:top;">
      <img src="https://www.example.com/email/logo-v2.png" width="120" height="40" alt="Example Co" style="display:block;border:0;">
    </td>
    <td style="padding:0 0 0 12px;border-left:2px solid #1a73e8;vertical-align:top;">
      <strong style="font-size:14px;color:#111111;">[Full name]</strong><br>
      [Job title], Example Co<br>
      <a href="tel:+15555550100" style="color:#1a73e8;text-decoration:none;">+1 555 555 0100</a><br>
      <a href="https://www.example.com" style="color:#1a73e8;text-decoration:none;">www.example.com</a>
    </td>
  </tr>
</table>

Export the logo at twice the display size (here 240 by 80 pixels) for sharp screens; Patronum’s help gives the same advice (Patronum Help). Google recommends signature images 70 to 100 pixels high by 300 to 400 pixels wide, with a maximum of 100 by 1,000 (Gmail Help). More in our email signature image size guide.

Before anyone else uses it, send it from Gmail and open the received message in Gmail, classic Outlook for Windows and new Outlook. Expect a pasted signature to change slightly: in our 13 Nov 2026 test, Gmail’s signature editor removed role="presentation" and the default Arial font-family on paste, while keeping the other inline styles.

Which HTML and CSS hold up when the email arrives?

Inline styles on tables, text and images hold up. Anything that depends on a <style> block, a linked stylesheet or a downloaded font doesn’t. A signature sits inside the message body, and Can I email, the email client support database, records Gmail’s <style> support as partial, with no support inside the body (Can I email). Class-based styling goes with it.

The table below describes how Gmail and classic Outlook for Windows (Can I email’s tests of Outlook 2007 to 2019) display HTML in a received message. It isn’t a test of what survives Gmail’s signature editor, a clipboard paste or the Gmail API, and Can I email doesn’t list new Outlook for Windows separately. Data checked 13 Nov 2026.

Feature	Gmail (web)	Classic Outlook for Windows	What to do
`<table>` layout	Supported	Supported	Use tables for columns (source)
`<style>` block and classes	Not inside the body	Buggy	Put every style inline (source)
Linked CSS (`<link>`)	Not supported	Supported	Don’t link stylesheets (source)
Web fonts (`@font-face`)	Not supported	Partial, remote fonts ignored	Use a safe font stack (source)
PNG and JPG images	Supported	Supported	Host them at a public URL (PNG, JPG)
SVG images	Rendered but rasterized to PNG (September 2026 test); not supported in earlier tests	2007 to 2016 no, 2019 yes	Export a PNG (source)
Base64 (data URI) images	Not supported	Not supported up to 2016	Host the file (source)
CSS background images	Supported	Not supported (VML only)	Don’t put text over an image (source)
`border-radius`	Supported	Not supported	Expect square corners (source)
`display:flex`	Supported	Not supported	Use table cells (source)
`padding`	Supported	Table cells only	Pad `<td>`, not `<div>` (source)

Is there a character limit for Gmail signatures?

Yes. Google’s help puts the limit at 10,000 characters (Gmail Help). For HTML signatures, count the code, not the visible text: Patronum’s help says the limit covers the HTML itself, including CSS and links (Patronum Help). Keep the finished HTML under 10,000 characters. If a signature is already failing, see Gmail signature too long or not showing.

What happens to an HTML signature in dark mode?

It depends on the app reading the email. In Can I email’s tests, Gmail doesn’t support the @media (prefers-color-scheme) method on web or mobile (Can I email). Litmus’s dark mode chart (February 2025) lists the Gmail app on iOS as fully inverting colors, the Android app as partially inverting them, and Gmail on desktop as making no change (Litmus). So:

Use a logo PNG with a transparent background and a subtle outline or light padding, so a dark logo doesn’t vanish.
Keep text out of images, since the app can’t recolor it.
Pick mid-tone link colors that stay readable when inverted.

How does Outlook show a signature sent from Gmail?

It depends which Outlook. Classic Outlook for Windows uses its own older rendering rules, so a signature that looks right in Gmail can lose rounded corners, background images and some spacing (see the table). Classic Outlook also blocks automatic picture downloads from the internet by default (Microsoft Support). New Outlook for Windows isn’t covered by those tests, so test it separately. Either way, keep your name, title and phone number as real text, so the signature still works with images blocked.

How Patronum handles HTML signatures

Patronum, a Google Workspace management platform, lets admins build one HTML signature, fill it from Google Directory fields and apply it to users’ Gmail by policy through the Gmail API. Its editor has a visual view and a source option for raw HTML (Patronum blog), and the product page describes an advanced HTML editor for custom designs (Patronum).

Patronum policy SIGNATURE tab editor toolbar with Font, Formatting and Font size menus, a Source button, Personal, Policy, Company and Social placeholder menus and a Conditions button — The signature editor on a policy’s SIGNATURE tab in the Patronum console, with a Source button, placeholder menus and Conditions. The side panel offers templates to start from.

Template from Directory data. Placeholders such as {{fname}}, {{jobTitle}} and {{phone}} are filled from each user’s Google Directory profile (Patronum Help).
Conditions for missing fields. A condition can check whether an attribute is empty, not empty or contains a value and show other HTML, such as the company phone when a user has no work phone (Patronum Help).
Size check. Patronum warns as the HTML nears 10,000 characters but still lets you save, since conditions can shorten each user’s final code.
Scope and activate. Target everyone, an organizational unit or a Google Group.

Patronum syncs signature policies to Gmail hourly, and Gmail may cache signatures for 1 to 2 hours (Patronum Help). If a user edits their signature by hand, the policy overwrites the change on the next sync.

FAQ

Can I paste HTML code directly into Gmail’s signature box?

No. The box is a formatted text editor, so code shows up as text. Open the HTML in a browser, copy the rendered signature and paste that, or have an admin set the HTML through the Gmail API.

Why does my HTML signature look different in Outlook?

Usually because it’s classic Outlook for Windows, which doesn’t support rounded corners, CSS background images or display:flex, pads only table cells and blocks automatic picture downloads by default. New Outlook for Windows behaves differently, so test both.

Can I use an SVG logo in a Gmail signature?

It’s a poor choice. In Can I email’s September 2026 test, Gmail rasterized SVG to PNG, classic Outlook 2007 to 2016 didn’t show it, and Patronum doesn’t support SVG in signatures. Use a PNG at twice the display size.

If you manage signatures for a whole Google Workspace domain, Patronum’s email signature management lets you keep one HTML template, fill it from Directory data and apply it by policy, with a 30-day free trial.