What is a mailto: URI?

A mailto: URI, defined in RFC 6068, is a link that opens the user's email client with a new message pre-filled. Putting it in an anchor's href lets a click compose an email to a chosen address with an optional subject and body.

How are spaces and line breaks handled?

All header values are percent-encoded. Spaces become %20 and a line break becomes %0D%0A (a carriage return plus line feed), which is the correct sequence for the body of a mailto link so paragraphs render properly.

Can I add Cc and Bcc?

Yes. Cc and Bcc are added as query parameters after the subject and body, each holding one or more comma-separated addresses. Bcc recipients are not shown to other recipients when the message is sent.

Why is the subject encoded but the email address mostly not?

The address sits in the URI path and only its reserved characters are escaped, while the subject and body are query values where spaces, ampersands and other characters must be percent-encoded so the link parses correctly.

No. The mailto link is assembled entirely in your browser, so nothing you type is sent to a server.

Mailto URI Encoder — Gera Tools

The mailto: URI encoder builds a valid RFC 6068 mailto: link from a recipient list plus optional Cc, Bcc, subject and body. Each field is percent-encoded correctly so the link survives in HTML, QR codes and chat messages, and opens the user’s mail client with everything pre-filled.

How it works

A mailto link has the form mailto:address?key=value&key=value. The To addresses sit before the ?; additional recipients and the message use query parameters cc, bcc, subject and body. RFC 6068 requires that values be percent-encoded: every byte that is not an unreserved character is replaced with % plus its two-digit hex code.

The encoder uses encodeURIComponent for each value, then fixes the special cases the standard calls out — line breaks in the body must be %0D%0A, and a few characters are left readable. Parameters are joined with &. Empty fields are omitted, so a To-only link is simply mailto:[email protected].

Example

To:      [email protected]
Subject: Hello there
Body:    Line one
         Line two

Output:  mailto:[email protected]?subject=Hello%20there&body=Line%20one%0D%0ALine%20two

Notes

Most mail clients respect To, Cc, Subject and Body; Bcc support varies by client. Keep bodies short — some browsers cap URL length, and very long pre-filled messages may be truncated. The output drops straight into <a href="mailto:...">. Everything runs locally; nothing you type is uploaded.