Generating URLs to a Gmail compose window#

I wanted to send out a small batch of follow-up emails for workshop attendees today, and I realized that since I have their emails in a database table I might be able to semi-automate the process.

I guessed that Gmail might have a way to generate a querystring URL to the compose interface such that the to/subject/body fields were filled out for me.

I ran prompts through ChatGPT, Claude and Google Gemini - in my experience LLMs often know about undocumented URL patterns like this.

The answer I got back turned out to work, but was out-of-date (it redirected to something different). Here’s what I figured out as the current correct format:

https://mail.google.com/mail/u/0/?to=recipient@example.com&cc=one@example.com,two@example.com&bcc=bcc@example.com&su=Email+Subject&body=Hello+There&tf=cm

Or more clearly formatted:

1
https://mail.google.com/mail/u/0/
2
  ?to=recipient@example.com
3
  &cc=one@example.com,two@example.com
4
  &bcc=bcc@example.com
5
  &su=Email+Subject
6
  &body=Hello+There
7
  &tf=cm

The tf=cm parameter at the end is the one that navigates to a compose window.

The query string parameters are:

to - the recipients - can be comma separated
cc - CCs - can also be comma separated
bcc - BCCs - can also be comma separated
su - the email subject
body - the initial email body

What this gets you#

Screenshot of a Gmail compose window. The To, CC, BCC, Subject and Body are filled out as requested in the URL.

Tip about the /u/0/ bit#

Tip from Corentin Smith:

You can replace the /u/0/ with /u/youremail@gmail.com/, it will redirect you to the correct account

It doesn’t work on Mobile Web#

Frustratingly, attempting to click one of these links in Mobile Safari takes you to the Gmail inbox but does not open a compose window. I don’t know if there’s a workaround for that.

The answer from Gemini#

My prompt was:

I would like to build an application that helps me send out emails by constructing URLs to the Gmail interface in the way that will pre-fill the to and cc and subject and body fields for me

Show me an example URL like that and then give me a table, documenting all of the query string parameters that I need to know

Google Gemini gave me this example:

https://mail.google.com/mail/?view=cm&fs=1&to=recipient@example.com&cc=someoneelse@example.com&su=Email%20Subject&body=Hello%20There

Following that link redirected to almost the example I provided above.

Gemini also gave me this table:

Parameter	Description	Example
`view`	Required. Sets the view mode to compose (`cm`)	`view=cm`
`fs`	Required. Fullscreen mode (`1` for on, `0` off)	`fs=1`
`to`	The recipient’s email address	`to=recipient@example.com`
`cc`	Email address(es) to CC (separate by commas)	`cc=someoneelse@example.com`
`bcc`	Email address(es) to BCC (separate by commas)	`bcc=anotherperson@example.com`
`su`	The email subject (URL Encoded)	`su=Email%20Subject`
`body`	The email body (URL Encoded)	`body=Hello%20There`

That’s not entirely correct -the fs=0/1 option no longer does anything, and I found that view=cm should be replaced by tf=cm.