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

Understanding the Enigmatic Presence of "3D" in HTML Code

When examining the source code of a received email, you may encounter peculiar HTML elements like the ones you've encountered:

<td>
<p>This seemingly cryptic "3D" isn't actually related to three-dimensional rendering in the usual sense. Instead, it's an integral part of an encoding scheme known as "quoted-printable."</p>
<p>Quoted-printable encoding is used to ensure that non-ASCII characters, such as foreign language characters or symbols, can be accurately transmitted and displayed in emails. It works by representing each non-standard email octet (an 8-bit unit of data) as an equal sign (=) followed by two hexadecimal digits that correspond to the octet's value.</p>
<p>However, email transportation systems may sometimes interpret a standalone equal sign (=) as an indicator of quoted-printable encoding, requiring it to be encoded as well. To represent the "=" character in such scenarios, quoted-printable uses the hexadecimal value 3D, which is the ASCII code for "=". Therefore, the seemingly enigmatic "3D" you've observed is simply the result of the encoding process, ensuring that the equal sign is correctly interpreted and displayed in the recipient's email client.</p>
</td>

The above is the detailed content of What Does \'3D\' Mean in HTML Email Code?. For more information, please follow other related articles on the PHP Chinese website!