Base64 is not encryption — it's encoding. If you paste Hello into a Base64 encoder and get SGVsbG8= , no secret key was used. The algorithm just translates binary data into 64 printable ASCII characters so it can travel through text-only channels like email, JSON, and URLs.
Source: [Dev.to](https://dev.to/zhihu_wu_dea1d82af01a04d7/base64-decoded-what-actually-happens-when-you-hit-encode-1h06)