XML Base64 variants

Some XML schemas need opaque binary identifiers that remain valid as NMTOKEN or Name values. Instead of + and /, they swap the last two Base64 alphabet characters:

Both omit padding. They are rare compared with RFC 4648 and Base64URL, but appear in niche enterprise XML and legacy interoperability specs.

How to work with them here

1. Paste a suspicious value into the Base64 standard detector.
2. Convert to standard Base64 with normalization.
3. Or decode directly on Base64 decode after selecting the matching XML standard.

If your value contains - and _ only, it is more often Base64URL (JWT, OAuth) than an XML variant.