If I run this command:
curl -H apikey:helloworld -d url=http://0x0.st/-_xA.png api.ocr.space/Parse/Image
I get this result: B\ND6N
should be: BWD6N
I solved it by changing to OCREngine 2 Free OCR API
extra text extra text
Good idea! See also Missing 1st letter after OCR - #2 by admin