Free Outlook Signature Generator

Why generic signature generators break in Outlook

Outlook 2007 through Outlook 2019 and Outlook in Microsoft 365 on Windows render email HTML through Microsoft Word's HTML engine, not a browser engine. Word strips most modern CSS, treats `<p>` margins as zero, ignores `border-radius`, and refuses CSS positioning. A signature designed for Gmail (which uses a browser-style renderer) lands in Outlook as a misaligned grid with sharp-cornered buttons, missing padding, and broken image alignment.

This generator outputs Outlook-safe HTML — table-based layout, inline styles on `<td>` cells, HTML attributes (`bgcolor`, `width`, `height`, `align`) alongside CSS for the parts Word reads, and MSO conditional comments that wrap Outlook-only fallbacks. It also produces a downloadable `.htm` file you drop directly into Outlook's Signatures folder, bypassing the settings UI entirely. No other free tool does either of those things.

The three Outlooks you are actually designing for

Outlook is not one product. Microsoft ships three different rendering pipelines under the Outlook name, and a signature that renders correctly in one will not necessarily render in the others.

Our renderer outputs HTML that works in all three. The Word engine reads the table-based layout and inline-styled `<td>` cells. WebView2 and WebKit read the same HTML and additionally honor the CSS that Word ignores (`border-radius`, `box-shadow`, etc.) — they get a slightly prettier result. There is no separate code path; the same HTML degrades gracefully across all three engines.

MSO conditional comments, in plain English

MSO conditional comments are HTML comments that only the Word engine renders as live HTML. Every other email client treats them as ordinary HTML comments and skips them.

<!--[if mso]>
  <table cellpadding="0" cellspacing="0" border="0">
    <tr><td>Outlook-only content</td></tr>
  </table>
<![endif]-->

<!--[if !mso]><!-->
  <div>Everyone else sees this instead</div>
<!--<![endif]-->

These come up most often for two things in signatures: rendering button backgrounds (Word strips `<a style="background:…">` but reads VML `<v:roundrect>` inside an `[if mso]` block) and forcing pixel-perfect widths (Word ignores CSS `max-width` but reads `width` attributes on tables inside `[if mso]` wrappers). Our generator emits these conditionals automatically where they matter — you do not write them yourself.

The drop-in .htm install method on Windows

Outlook stores signatures as `.htm` files in a specific folder. Drop a properly-formatted `.htm` file into that folder, restart Outlook, and the signature appears in the signature picker — no copy-paste, no Word filter, no layout corruption.

The install path on Windows:

%APPDATA%\Microsoft\Signatures\<your-signature-name>.htm
%APPDATA%\Microsoft\Signatures\<your-signature-name>_files\image001.png

A few details that matter:

• The extension must be `.htm`, not `.html`. Outlook only picks up `.htm` files from this folder. Save as `.html` and Outlook ignores it.
• Images go in a sibling folder. If your signature includes embedded images, Outlook expects them in `<signature-name>_files\` alongside the `.htm`. We host images externally (via imgbb) so you do not have to set up the `_files` folder for our generated signatures.
• You need to restart Outlook after dropping the file. New signatures in the folder are picked up on launch.

To paste the `%APPDATA%\Microsoft\Signatures\` path into Windows Explorer's address bar and hit Enter, Windows resolves the variable to the actual folder (usually `C:\Users\<you>\AppData\Roaming\Microsoft\Signatures\`).

How to tell which Outlook you have: in Classic, the top-left logo is the older yellow envelope and the top toolbar reads File / Home / Send / Receive. In New Outlook, the toolbar is condensed into a slim top bar with the new Microsoft 365 logo and a 'New Outlook' toggle in the top-right corner.

The drop-in install method on Mac

Classic Outlook for Mac uses a similar folder under your Library:

~/Library/Group Containers/UBF8T346G9.Office/User Content.localized/Signatures.localized/

The Outlook for Mac sandbox structure under `Group Containers/UBF8T346G9.Office` was introduced with the Microsoft 365 Outlook for Mac rollout. Drop the same `.htm` file we generate into this folder, restart Outlook, and it appears in the signature picker.

Fixing the 120 DPI / HiDPI image scaling bug

Windows display scaling above 100% (most modern laptops default to 125% or 150% on HiDPI screens) makes Outlook render signature images larger than their stated pixel width. A `<img width="150">` shows up as 188 pixels at 125% scaling, 225 pixels at 150%. This is one of the most-asked-about Outlook signature problems on Microsoft Q&A and Stack Overflow.

The root cause: Word's rendering engine multiplies image pixel widths by the system DPI ratio. The standard fix is to tell Word to treat the document as 96 DPI explicitly, via the `OfficeDocumentSettings` block in the document head. Our generated `.htm` file includes this block automatically:

<!--[if gte mso 9]>
<xml>
  <o:OfficeDocumentSettings>
    <o:AllowPNG/>
    <o:PixelsPerInch>96</o:PixelsPerInch>
  </o:OfficeDocumentSettings>
</xml>
<![endif]-->

With that block in place, images render at their stated width regardless of the Windows display scaling setting. Reference: Courtney Fantinato's canonical post is the most-cited write-up of the bug and the fix.

Images: external hosting vs. embedded, and why your logo shows as an attachment

Outlook supports three ways to include an image in a signature: external URL (the image lives on the web), embedded (the image lives in the `_files` folder next to the `.htm`), and inline base64 (the image bytes are pasted into the HTML itself).

• External URL. Easiest — our generator does this via imgbb. Outlook downloads the image on send and the recipient sees it inline. Downside: recipients with images blocked see a placeholder until they click Show Images.
• Embedded via `_files` folder. Outlook references the image as `cid:image001@…` in the HTML and attaches the image to the outgoing message. Recipients see the image without needing to enable images. Downside: every email you send now carries the embedded image as an attachment, inflating message size.
• Inline base64. Encodes the image bytes directly into the HTML. Works in some clients, breaks in Outlook desktop (Word strips long base64 strings). Avoid.

Multiple signatures across multiple Outlook accounts

Outlook supports multiple signatures and lets you assign different ones to different accounts (work, personal, "Send as" delegations). The path in Classic Outlook:

1. File → Options → Mail → Signatures.
2. In the top dropdown, pick the email account this signature applies to.
3. Click "New", give the signature a name, then either paste the HTML from our generator or — for the cleanest result — close this dialog, drop our generated `.htm` file directly into `%APPDATA%\Microsoft\Signatures\`, and Outlook will list it automatically when you reopen the dialog.
4. Set "New messages" and "Replies/forwards" defaults per account.

New Outlook (the WebView2-based redesign Microsoft has been rolling out since 2024) supports roaming signatures — your signature follows the account across devices and Outlook installs. Classic Outlook stored signatures locally per machine. If you have set up a signature in Classic and switched to New, the signature may not migrate; re-import the `.htm` file in New Outlook.

Classic Outlook vs New Outlook — what changes for signatures

If you are not sure which Outlook your colleagues are using, design for Classic. The HTML that works in Classic also works in New (and Mac, and the web client). The reverse is not true.

Troubleshooting checklist