What Does \'3D\' Mean in HTML Email Rendering?

"3D" in HTML: What Does It Mean in Email Rendering?

Have you ever encountered HTML code in a mailer that contains strange sequences of "3D"? These sequences may appear within attributes, leaving you wondering about their significance.

What Is "3D" in HTML?

The "3D" in HTML you observed is not related to 3D graphics but is instead an integral part of email rendering. It is a character sequence used in "quoted-printable" encoding.

Purpose of Quoted-Printable Encoding

Quoted-printable encoding is an email encoding system that allows non-ASCII characters to be represented in a format suitable for email transmission. Non-ASCII characters, which include accented characters, foreign alphabets, and special symbols, can cause issues when sent through email as they may not be recognized by all mail clients.

How Quoted-Printable Encoding Works

Quoted-printable encoding works by converting non-standard octets in email (values less than 32 or greater than 126) into a "3D" followed by two hexadecimal digits representing the octet's ASCII value.

Example of 3D in Quoted-Printable Encoding

For example, the equals sign (=) has an ASCII value of 61. To represent it in quoted-printable encoding, we would use "3D" followed by the two hexadecimal digits "61":

= -> 3D

Displaying the Equals Sign in Email

To display the equals sign correctly in an email, it also needs to be encoded:

= -> 3D
3D -> 3D3D

Conclusion

Therefore, the "3D" sequences you encountered in the HTML code of your mailer are part of quoted-printable encoding, which allows non-ASCII characters to be represented safely for email transportation. By understanding the purpose of quoted-printable encoding, you can now more effectively interpret and work with HTML code in emails.

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