Disclosure: I work on OnePassApps. This is our own app, and every line below was read or run in the live build on 6 November 2026.

An email signature is one of the few pieces of HTML that has to survive a mail client's editor, a dark-mode rewrite and a paste into a settings page. So the useful questions are narrow: what does the generator actually produce, what does it refuse to produce, and what happens to the copy button when a field is wrong.

OnePassApps ships an Email Signature Builder at app.onepassapps.com/apps/email-signature. The page says it plainly: "Create a signature locally, then copy it into your mail client. Example details are editable; nothing is saved or uploaded." and, lower down, "Nothing leaves this tab."

The three stages

The builder is 01 Content, 02 Style, 03 Export.

Content asks for Full name, Job title, Company, Phone number, Email address and Website URL, plus an Address and a Closing line that are both marked Optional. The website field carries the hint "Include https://. Only website links are accepted."

Style has a Layout choice of Accent line or Classic, and an accent colour, with the guidance "Choose a dark colour for legibility on light mail backgrounds." The default I measured was #176b62.

Export has a Format choice of Formatted, HTML file and Text file. Under Formatted the page explains: "Formatted, for mail apps: paste it into your signature settings."

The validation that pauses the copy buttons

I typed a deliberately broken email address into Email address. The page answered "Email address needs attention. Copy and download are paused until it is fixed." and showed the field hint "Enter a valid email address or leave it blank." While that state was showing, the three export controls - Copy plain text, Copy HTML source and Copy signature - were all disabled. I replaced the address with a valid one and all three enabled.

That is the detail worth knowing: the tool does not hand you a broken mailto link. It stops the copy step and tells you which field is wrong.

What the plain-text output looks like

With a name, job title, company, email, website, phone and a closing line filled in, the plain-text signature came out as six short lines - name, job title and company joined by a middle dot, email, phone, website, closing line. In my run it was 135 characters.

What the HTML output looks like

960 characters, and it is a table rather than a stack of divs:

<table role="presentation" cellpadding="0" cellspacing="0" border="0" style="font-family:Arial,Helvetica,sans-serif;font-size:14px;line-height:22px;color:#252525;width:100%;max-width:600px;table-layout:fixed;"><tbody><tr><td style="border-left:3px solid #176b62;padding-left:14px;overflow-wrap:anywhere;word-break:break-word;"><strong style="font-size:18px;line-height:24px;color:#176b62;">OnePassApps</strong>...

The name sits in a strong tag at 18px on a 24px line in the accent colour. The job title and company are a plain span, the email and the website are anchors, and the closing line is an italic span. The table is capped at 600px with table-layout:fixed, and the cell carries overflow-wrap:anywhere and word-break:break-word, so a long address cannot stretch the table sideways.

A table is the safe choice for mail clients: they still render tables the most predictably, which is the reason to expect this output to paste cleanly - though I did not paste it into a real mail client.

I clicked the Classic layout control and the HTML I could read back was unchanged, so I am not going to describe the second layout - I could not measure a difference from the output I had.

The paste steps the app prints

Under ADD IT TO YOUR MAIL CLIENT the page carries a mail-client chooser (Gmail on the web in my run) and three steps: select Copy signature, open Settings then See all settings then General then Signature then Create new, then paste and save. Two caveats are printed by the app itself: "Menus vary by version. No external images or tracking pixels are included." and a collapsible "If formatted copy is blocked" that I did not open, so I will not paraphrase what is inside it.

The preview panel has a MESSAGE BACKGROUND switch, Light and Dark, and is honest about what it is doing: "Dark approximates how dark-mode mail apps recolour a message. Send yourself a test to be sure."

Did anything leave the tab?

I turned on the browser's network trace, filled the form, switched the layout and switched the export format. The page made six requests in that window and not one of them carried a request body. The hosts it did talk to were its own app API and the sign-in service it uses. The signature text itself never left the tab.

What I did not measure

  • I did not open the "If formatted copy is blocked" panel.
  • I did not test the HTML file and Text file exports - I measured the Formatted output only.
  • In one run a sign-in prompt appeared over the page while I was switching the preview tabs, so I did not measure what the copy buttons put on your clipboard, and I am not claiming it.
  • I tested the paste steps for Gmail on the web, because that is the client the page prints.

The plan block

The same page carries the current plan: Standard is free right now, "$0 / month", "100,000 credits every 30 days", no card required and no automatic paid subscription. App guides are at app.onepassapps.com/guides.

I work on OnePassApps, and every measurement above comes from the build we ship today.