The full Gmail signature setup — desktop, mobile, aliases, Google Workspace. Plus the image rendering, font mangling, and reply quirks that break signatures in production.
The MailSigCraft Team
MailSigCraft
Gmail stores email signatures in four different places depending on how you use it: the web app, the iOS and Android apps, send-as aliases, and Google Workspace admin-pushed templates. Each has its own quirks, and a signature that works perfectly in the web app will often render wrong on mobile, disappear on replies, or get overridden by Workspace policy. This guide covers the full setup, then the eight specific things that break in production.
If you just want the steps, the Gmail install guide has the clean seven-step version with screenshots. This post goes deeper.
That's it for 90% of users. The remaining 10% run into one of the problems below.
Gmail treats signatures as rich HTML embedded in the compose body, not as a separate layer like Outlook does. That design choice has three consequences that catch people out:
cid: attachments (or doesn't, depending on the account), and may rewrite font stacks to match its own allow-list.The most common issue. Gmail handles signature images in two different ways depending on where the image is hosted:
If you pasted a signature from another tool and images are broken, the fix is to re-generate it from a tool that base64-embeds, or host the images on a reliable CDN with proper CORS headers.
Check the "Signature defaults" dropdowns in Gmail settings. There are two separate dropdowns — For new emails use and On reply/forward use — and Gmail defaults the second one to "No signature". Set both to the same signature.
When you reply to an email, Gmail inserts your signature below the quoted thread, not inline. If your signature looks weirdly spaced, it's because Gmail added line breaks before it. There's a checkbox in settings labelled "Insert signature before quoted text in replies" — tick that, and your signature will sit directly above the quoted message instead of at the very bottom.
Gmail has a limited font allow-list for signatures: Arial, Verdana, Trebuchet MS, Times New Roman, Georgia, Garamond, Helvetica, Courier New, Tahoma, Narrow, Comic Sans, Impact, Sans Serif, Serif, Wide, Monospace. Anything else (custom brand fonts, Google Fonts, web fonts) gets silently swapped for Gmail's default sans-serif at send time.
The fix is to pick from the allow-list at signature design time. MailSigCraft's font picker only shows email-safe fonts for this reason.
This is the signature-generator trap. A tool that only tests in Gmail's web view will produce HTML that relies on CSS properties Outlook 2019 and Apple Mail don't support. When you send the email, the recipient's client renders it differently.
Common offenders: flexbox layouts (Outlook uses Word's rendering engine, which pre-dates flexbox by a decade), <div>-based structures (table-based HTML is still the lingua franca of email), and modern CSS (calc(), CSS variables, object-fit).
The only way to catch this is to actually test in every client you care about — which is why MailSigCraft uses table-based layouts and tests every template across 14+ clients before shipping.
Gmail on iOS and Android doesn't support HTML signatures at all. Whatever you set in Settings → Your account → Signature settings in the mobile app is a plain-text signature, and it's the one that gets appended to emails you send from mobile.
If most of your email comes from your phone, the realistic choice is: (a) accept that mobile signatures are plain text and use them as such, or (b) always write from desktop for branded emails.
If you use Gmail's "Send as" feature to send from multiple addresses (yourname@company.com, support@company.com, etc.), each alias has its own signature slot in the Signature defaults section. Setting one doesn't set the others. This is a feature, not a bug — you likely want different signatures per alias — but it catches people who think they've set it site-wide.
If your company uses Google Workspace, your admin may have enabled "Append footer" in the Gmail admin console. When that's on, the admin's template is appended to every outgoing email regardless of what you set personally. Some admins configure it as replace rather than append, in which case your personal signature is silently ignored.
There's nothing you can do from the user side — it's an admin-level policy. If you're the admin and you want personal signatures to work, either disable the append footer or switch to a signature-management tool that integrates with Workspace (MailSigCraft's Team plan is one option).
Send an email to yourself. Not a test email to a coworker — to yourself, at a different address (personal Gmail, iCloud, whatever). Open it on desktop webmail, on the native mail app on your phone, and in an Outlook account if you have one.
Three things to check:
javascript: pseudo-links that mail clients strip.If all three pass on all three clients, your signature is good.
Gmail ships UI changes every few months, and the Workspace admin surface changes on its own cadence. If your signature suddenly breaks without you changing anything, check the "Last updated" date on this post — we keep the steps current as the UI shifts.
Full install guide with screenshots: mailsigcraft.com/install/gmail.