Sven, with the code you suggested add: aFilePath ^ZnClient new url: prefix , '/add?stream-channels=true'; addPart: ((ZnMimePart fieldName: 'file' fileNamed: aFilePath) headers contentType: ZnMimeType default); post. and invoking ipfs add: 'file.txt' I get HTTP/1.1 User-Agent: Zinc HTTP Components 1.0 Content-Length: 176 Host: 127.0.0.1:5001 Content-Type: multipart/form-data;boundary=Boundary-Zn-BCJQCIUT Accept: */* --Boundary-Zn-BCJQCIUT Content-Disposition: form-data;name="file";filename="file.txt" Content-Length: 16 Content-Type: application/octet-stream --Boundary-Zn-BCJQCIUT-- Very good! Thanks a lot. ----- http://chicoary@gmail.com -- View this message in context: http://forum.world.st/How-to-generate-Content-Type-application-octet-stream-... Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com.