As of October 23, 2026, Signatoro, the agentic email signature platform, is listed in ChatGPT's plugin directory: Signatoro in ChatGPT. Install it once and add the email signature rule to ChatGPT's custom instructions, and before ChatGPT drafts or sends an email for you, it fetches your saved signature and ends the email with the current version. Until now, connecting ChatGPT to Signatoro took developer mode. The listing replaces that with an Install button.
Signatoro has been in Claude's connector directory since October 13, so ChatGPT and Claude now fetch the same saved signature. Change it once on Signatoro, and the next email either one signs carries the change.
Tested: a ChatGPT draft that ends with the saved signature
We tested the plugin in ChatGPT on October 23, 2026, on a Free account, right after installing it. We asked ChatGPT to fetch the saved signature and draft a short email. ChatGPT called Signatoro, showed "Retrieved the latest email signature", and ended the draft with the signature exactly as saved: name, title, email, website and a reviews link.
Install Signatoro in ChatGPT in three steps
- In ChatGPT, open "Plugins" in the sidebar and find Signatoro, or open the listing linked at the top of this post.
- Click "Install plugin".
- Sign in to Signatoro when ChatGPT asks you to connect your account, the first time you use it.
To have ChatGPT sign every email, open "Settings", then "Personalization" on the web ("Customize ChatGPT" in "Settings" in the app), and paste the email signature rule into "Custom Instructions". Without the rule, ChatGPT signs an email when you ask it to.
The ChatGPT guide covers the other routes: email you copy from ChatGPT into Gmail or Outlook, and agents you build on the OpenAI API.
Why ChatGPT fetches your signature
On paid plans, ChatGPT drafts and sends email through the Gmail or Outlook app you connect to it, on the web. That email is written in ChatGPT, and Gmail and Outlook add your signature only in their own compose windows. Without Signatoro, the email ends with whatever sign-off ChatGPT writes, or a copy pasted into its instructions that stays as it was until you paste again.
With the plugin, ChatGPT calls get_signature and gets three things:
- Your signature as text and HTML. The text version is the reliable one for email ChatGPT sends: Signatoro has found that the Gmail tool in chat assistants drops images from the HTML it is given.
- Your real details as fields. Your name, title, phone, email and links come back as
sender, so when ChatGPT writes "call me at" in the body, it uses the number you saved. - The latest change. A new title or phone number shows up in the next email.
Your AI assistants sign as themselves
If more than one AI assistant sends email for you, each can have its own signature on Signatoro: yours with a line such as "Sent by Ada, my AI assistant", or the assistant's own name and role. The ChatGPT plugin signs with your own signature today. Its next version, in OpenAI's review, lets ChatGPT list your assistants' signatures and ask which one an email needs.
On a Company plan, the owner sets the logo, layout and colors once, and every person's and every company AI agent's signature carries them.
What else ChatGPT can do with Signatoro
Without an account:
- Make a free signature from your name and details, as HTML and text, with a link to save and edit it in Signatoro (
create_signature). - Compare the layouts (
list_templates). - Get the install steps for Gmail, Outlook, Apple Mail and 25+ other mail apps (
get_install_steps).
Signed in, change your saved signature ("update my title to Head of Design") with update_my_signature.
Company owners can list their people, invite someone with their name, title and phone, update a detail and resend an invitation.
Signatoro in ChatGPT questions
Is the Signatoro plugin free?
Yes. Making a signature works without an account, and a free account saves your signature for ChatGPT to fetch. Each get_signature call counts as one API request: Free has a monthly limit, and company plans are unlimited. See pricing.
Do I still need developer mode?
No. The plugin installs from ChatGPT's Plugins page. Developer mode still works if you prefer to add https://signatoro.com/mcp yourself, as the MCP guide shows.
Does Signatoro read my email?
No. Signatoro handles signature details and company people only. It never reads or stores your email.