How to add an email signature in Outlook 365 web
Outlook in the browser —Microsoft 365 at outlook.office.com and Outlook.com— stores the signature in your Microsoft mailbox. It is the easiest place to install it if your company runs Microsoft 365: you paste it once and it is saved in your account, not on one particular computer.
It lets you keep several named signatures and choose which one goes on new messages and which on replies. For a sales team it is handy to have a full version with the logo and a short one for long threads.
Steps in Outlook web
- 01
Copy your signature from SignatureForever with Outlook 365 as the destination.
- 02
In Outlook web, click ⚙ Settings at the top right.
- 03
Go to Account › Signatures. In some versions the menu is called Mail › Compose and reply.
- 04
Click “New signature”, type a name and paste the signature into the box with Ctrl+V or Cmd+V.
- 05
Under “Select default signatures”, choose that signature for new messages and for replies and forwards.
- 06
Click Save and close settings.
If your company also uses Outlook desktop, don't assume the signature is already there. Depending on how your admin set up Microsoft 365, the web signature may not travel to the classic app; check the Outlook desktop guide.
Because the signature lives in your mailbox and not on a specific machine, it travels with you when you open Outlook from your laptop at home, a borrowed computer or a hotel browser on a trip. For companies that want the same for all staff, the Teams plan includes Microsoft 365 sync.
A test routine that works: send one email to a Gmail account, another to an Outlook account, and open them on your phone too. Those are three different screens and each one reveals something the others hide. If all three look right, your signature is ready for clients and suppliers.
What breaks in Outlook 365 web and how to avoid it
Outlook web is more forgiving than its desktop sibling, but it is not fully modern. Flex, grid, the <style> block and background-image work halfway: sometimes yes, sometimes no, depending on how the email is opened. Web fonts never load. On the other hand, it does show base64 images, which leads many people to think their signature is fine until someone sees it in Gmail.
The practical move is not to bet on what works halfway. If your signature needs columns, build them with table cells; if it needs spacing, use padding inside the cell; if it carries an image, make it an <img> with dimensions. That way it looks the same in Outlook web, Outlook desktop and Gmail.
| Feature | Outlook 365 web |
|---|---|
| <table> layout | Yes |
| display:flex and CSS grid | – Partial |
| <style> block in the head | – Partial |
| background-image in CSS | – Partial |
| Images as data URI (base64) | Yes |
| border-radius | Yes |
| letter-spacing | Yes |
| text-transform:uppercase | Yes |
| Web fonts (Google Fonts) | × No |
| max-width and percentage widths | Yes |
| margin on <td> | – Partial |
| <img> without explicit width and height | – Partial |
In total: 1 unsupported, 5 partial and 6 fully supported, out of the 12 features in the matrix. Why each one fails, in the full matrix.
Common mistakes
Pasting into the message body
Pasting the signature at the end of an email works once. If it doesn't go through Settings › Signatures, it won't be added to the next one.
Not choosing a default signature
Creating the signature isn't enough: if “New messages” still says “(no signature)”, you have to insert it by hand every time.
Only testing between Outlook accounts
Outlook web shows things Gmail doesn't. Send the test to a Gmail account as well.
Frequently asked questions
Where are signatures in the new Outlook web?
Under ⚙ Settings › Account › Signatures. If your version doesn't have that menu, look under Mail › Compose and reply.
Why does my font look different in Outlook web?
Because it doesn't load web fonts. Use a safe font like Arial, Georgia or Verdana and it will look the same everywhere.
Can I have a short signature for replies?
Yes. Create two signatures and in the defaults pick the full one for new messages and the short one for replies.
Are you an AI agent? This is also available as an MCP server at signatureforever.com/mcp