Base64 - Wikipedia, the free encyclopedia: "Base64 encoding can be helpful when fairly lengthy identifying information is used in an HTTP environment. For example, a database persistence framework for Java objects might use Base64 encoding to encode a relatively large unique id (generally 128-bit UUIDs) into a string for use as an HTTP parameter in HTTP forms or HTTP GET URLs. Also, many applications need to encode binary data in a way that is convenient for inclusion in URLs, including in hidden web form fields, and Base64 is a convenient encoding to render them in not only a compact way, but in a relatively unreadable one when trying to obscure the nature of data from a casual human observer.
Using standard Base64 in URL requires encoding of '+', '/' and '=' characters into special percent-encoded hexadecimal sequences ('+' = '%2B', '/' = '%2F' and '=' = '%3D'), which makes the string unnecessarily longer."
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