The JWS standard* has two different representation ("serialization") formats:
The Compact Serialization, which uses base64 encoding with dot concatenation of header, body and signature ("eyX.Y.Z"). See RFC 7515 section 3.1.
The JSON Serialization, which uses JSON encoding of the base64 encoding of header, body, and signature ("{"protected": "eyX", "payload": "Y", signature: "Z"}"). See RFC 7515 section 3.2
Which of these two serialization formats is used varies in different protocols. RFC 8555 Section 6.2 requires JSON serialization, so the latter of the two.
*In a broader context, the two serialization schemes exist for most JSON Web Algorithms (JWA) formats, not only JWS.
This is what I'm posting... (Strip line breaks)
{"protected":"eyJhbGciOiJFUzI1NiIsImp3ayI6eyJrdHkiOiJFQyIsImNydiI6IlAtMjU2IiwieC
I6ImdTbWU5cmMweUFGN18wX2lDY0V1cENNYUt2bkdRU0JFZHZQbkRQUTFlXzAiLCJ5IjoiRXByQ21vYl
ZfRG1hZWdVOTNSWWp1d1VjTExwTjNBd0xpUlJvQlFBSWJZUSJ9LCJub25jZSI6IjJRb1pjWUdYZUtuZ2
VHaHBNMUJ1Q25jS0pqZEZGb1l0U3hQRDdPY1ZoTk5ZeFZsMGYwOCIsInVybCI6Imh0dHBzOi8vYWNtZS
1zdGFnaW5nLXYwMi5hcGkubGV0c2VuY3J5cHQub3JnL2FjbWUvbmV3LWFjY3QifQ","payload":"eyJ
0ZXJtc09mU2VydmljZUFncmVlZCI6dHJ1ZX0","signature":"a0hZQs92IHtKNWHuhujCfsFZ_LlrE
QmD6cZ_3cWcteICnrZyYCviHMqKgzat8L7KsIQfu-w9on7jyaZYavRImQ"}