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When you send an email with an image, PDF, or even emojis, your email client does a bit of magic behind the scenes—converting binary data into text using something called Base64 encoding. For many developers and IT professionals, understanding how this works (and how to decode 64 data) is key to debugging and maintaining reliable email systems.

MIME, short for Multipurpose Internet Mail Extensions, is the protocol that allows emails to handle more than just plain text. Before MIME, you couldn’t send attachments or rich HTML content. But binary data—like images or PDFs—can’t travel through text-only systems. That’s where Base64 comes in. It transforms binary data into a text-friendly format made of readable ASCII characters.

When your email client receives this encoded data, it performs the reverse—decode 64—to restore the original attachment or image. This process ensures that no data gets corrupted in transit and that every part of your email reaches safely and intact.

Developers testing email APIs or automation systems often need to simulate this encoding-decoding behavior. That’s where tools like Keploy become helpful. Keploy can automatically record API traffic, including Base64 payloads, and generate test cases and mocks that help verify encoding integrity during testing.

Understanding how MIME and decode 64 processes work doesn’t just make you better at troubleshooting email-related issues—it deepens your appreciation for the systems keeping digital communication seamless.